Eric Collet

Professeur / Directeur-Adjoint

Eric Collet

E-mail : 

Téléphone :  +33 223236532

Bureau :  Bâtiment 11E / Etage 1 - 102

  1. What's new
  2. Research topics
  3. Publications
  4. Learn more

Eric Collet is professor of Physics and deputy Director of the Institut de Physique de Rennes.
He is studying photoinduced phase transitions in molecular materials and their ultrafast dynamics:

Eric Collet
  • from microscopic to macroscopic,
  • from electronic excitation to structural trapping.

  He is developping advanced structural studies, combined with ultrafast techniques:

He is member of the Institut Universitaire de France (IUF junior 2008-13). He has been awarded the 2017 Louis Ancel price of the French Physical Society for his achievements in condensed matter physics.

Eric Collet and Shin-ichi Okhoshi are the directors of the IM-LED international laboratory (France-Japan).

What's new


Our collaboration with Japan highlighted at the city hall of Rennes. Isabelle Pellerin (Rennes) and David Alis (President of UR1) underlined the important contributions of Prof Shin-ya Koshihara for the development of Japan-France collaborative programs and of Prof Shin-ichi Ohkoshi, who is co-director with Prof. Eric Collet of the International Laboratory IM-LED :



We organized the first edition of the "Ultrafast Control of Materials" school and symposium at
the University Rennes 1 from Monday 11th to Thursday 14th June 2018.

More than 80 researchers and students participated to the meeting.

UCM2018 gathered experts interested in the study of the control of the physical properties of materials with a special focus on ultrafast science. Topics covered during this meeting included recent advances in photoinduced phenomena, non-linear phononics, THz science, elastic cooperativity, strong electric field effects and X-FEL science. The goal of this meeting is to have intense and frank scientific exchanges in a very friendly atmosphere on the emerging topics appearing with new laser-based techniques for controlling and understanding materials at work. 


Learn more about the meeting here:

UCM2018 is supported by: the CNRS, Univ Rennes 1, the SFP, the ANR, the Université de Rennes 1, Université de Nantes, Université du Maine, Université de Versailles de Saint-Quentin-en-Yvelines, and four universities from Japan, the University of Tokyo, Tokyo Institute of Technology, Tohoku University, and Kyoto University. 


Louis Ancel Price of the French Physical Society


Eric Collet has been awarded the Louis Ancel price of the French Physical Society (SFP) in 2017 for his achievements in condensed matter physics. At this occasion, he will deliver a plenary talk during the JMC 2018 meeting in Grenoble.

Fast & Ferrous!




Electronic and structural dynamics during the switching of the photomagnetic complex [Fe(L222N5)(CN)2].
The [Fe(L222N5)(CN)2] compound is a photomagnetic FeII (ferrous) based coordination compound, which undergoes light-induced excited spin-state trapping (LIESST). The low spin state is hexacoordinated and the high spin state heptacoordinated. This system also serves as complex for the design of trinuclear or one-dimensional compounds made of other types of bricks with diverse coordinated metals. Here we study its ultrafast spin-state photoswitching dynamics, by combining femtosecond optical spectroscopy and femtosecond X-ray absorption measurements at the XPP station of the X-ray free-electron laser LCLS. DFT and TD-DFT calculations are used to interpret experimental findings. These studies performed in the solution phase show that LIESST in [Fe(L222N5)(CN)2] occurs on the 100 fs timescale under different types of photoexcitation. In addition, we observe coherent oscillations resulting from the structural dynamics accompanying LIESST, which were recently evidenced in more conventional octahedral FeIIN6 systems.

S. Zerdane, E. Collet,* X. Dong, S. F. Matar, H. F. Wang, C. Desplanches, G. Chastanet, M. Chollet, J. M. Glownia, H.T. Lemke, M. Lorenc, M. Cammarata,*
Electronic and structural dynamics during the switching of the photomagnetic complex [Fe(L222N5)(CN)2]
      Chemistry A European Journal doi 10.1002/chem.201704746 (2017)

This study is in direct relation with our paper publihed in Nature Communication:


Chemical Reviews: M. Chergui and E. Collet

Photoinduced structural dynamics of molecular systems mapped by time-resolved x-ray methods.

Chemical Reviews

We review the tremendous advances in ultrafast X-ray science, over the past 15 years, making the best use of new ultrashort x-ray sources including table-top or large-scale facilities. Different complementary x-ray based techniques, including spectroscopy, scattering and diffraction, are presented. The broad and expanding spectrum of these techniques in the ultrafast time domain, is delivering new insight into the dynamics of molecular systems, of solutions, of solids and of Biosystems. Probing the time evolution of the electronic and structural degrees of freedom of these systems on the timescales of femtosecond to picoseconds delivers new insight into our understanding of dynamical matter.

Chemical Science:
Comparison of structural dynamics and coherence of d-d and MLCT light-induced spin state trapping 

S. Zerdane, L. Wilbraham, M. Cammarata,* O. Iasco, E. Rivière, M.-L. Boillot, I. Ciofini, and E. Collet*

Chemical Science

Light Induced Excited Spin State Trapping (LIESST) in FeII spin-crossover systems is a process switching molecules from low (LS, S=0) to high spin (HS, S=2) states. The direct LS-to-HS conversion being forbidden by selection rules, LIESST involves intermediate states such as 1,3MLCT or 1,3T. The intersystem crossing sequence results in a HS state, structurally trapped by metal-ligand bond elongation through the coherent activation and damping of molecular breathing. The ultrafast dynamics of this process was so far investigated in FeN6 ligand field systems, under MLCT excitation. Here we study LIESST in an FeIIN4O2 spin-crossover material of lower symmetry, which allows quite intense and low-energy shifted d-d bands. By combining ab-initio DFT and TD-DFT calculations and fs optical absorption measurements we demonstrate that, compared to MLCT, d-d excitation induces faster LS-to-HS switching and that the shorter intermediates enhance coherent structural dynamics.

Nature Communication:

     Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

H. T. Lemke*, K. S. Kjær, R. Hartsock, T. B. van Driel, M. Chollet, J. M. Glownia, S. Song, D.  Zhu, E. Pace, S. F. Matar, M. M Nielsen, M. Benfatto, K. J. Gaffney, E. Collet, Marco Cammarata*

Nature Communication

The description of ultrafast nonadiabaticchemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear structures impact each other and cannot be treated independently. Here we gain new experimental insights, beyond the Born-Oppenheimer approximation, into the light-induced spin-state trapping (LIESST) dynamics of the prototypical [Fe(bpy)3]2+ compound by time-resolved XANES spectroscopy at sub-30-femtosecond resolution and high signal to noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period) clearly identified as molecular breathing. Throughout the structural trapping, the dispersion of the wave packet along the reaction coordinate reveals details of intramolecular vibronic coupling before a slower vibrational energy dissipation to the solution environment. These findings revisiting the LIESST process illustrate how modern time-resolved XANES provides key information to unravel dynamic details of photo-functional molecules.

International Laboratory between France and Japan:

News :
Univ. Rennes 1 :
Univ. Nantes :
Univ. Versailles St Quentin :
Tokyo Tech english :
Tokyo Tech Japanese :

Elastically driven cooperative response of a molecular material impacted by a laser pulse


Nature Materials



Order, better, spin cross-over

Work it harder, make it better, describe order, our work on spin-crossover (Daft Punk’s summary version!).

Hiroshi Watanabe, Koichiro Tanaka, Nicolas Bréfuel, Hervé Cailleau, Jean-Franǫis Letard, Sylvain Ravy, Pierre Fertey, Masamichi Nishino, Seiji Miyashita, and Eric Collet
Ordering phenomena of high-spin/low-spin states in stepwise spin-crossover materials described by the ANNNI model
Physical Review B 93 014419 (2016)



Research topics

In molecular materials, interactions brought into play result in fragile equilibrium between multistable states, switchable under the effect of temperature or pressure and we are investigating how light can switch them.


Photoinduced phase transition


Our team is investigating the mechanisms driving these switching at thermal equilibrium or in highly out-of-equilibrium dynamics by using state-of-the art techniques in our laboratory (photo-crystallography, ultrafast optical spectroscopy…) and also large facilities (X-FEL, synchrotron, …).

X-ray diffraction


The scientific issues deal with understanding and controlling switching between multi-stable states, in particular driven by light. The new field of photoinduced phase transitions deals with the study and the control of material’s response to light excitation. Indeed, light excitation, of continuous or pulsed nature, may induce the transformation materials towards another phase of different electronic/structural order. This new way of acting on matter combines many of today’s interconnecting issues such as far away from equilibrium phenomena, coherence and quantum control, correlated behaviour and nonlinear responsiveness, interconversion of energy and information, … These are  key elements for the advent of control science, where the challenge is not only to observe matter on ever smaller scale but also to direct its functionality at the relevant length, time and energy scales. Our knowledge in the study of complex materials or ordering phenomena is a strong input in the study of multi-stability.

Structural analysis and photo-crystallography

Ultrafast diffraction


Femtosecond pump-probe experiment: ultrafast photo-switching

Femtosecond laser

Ultrafast crystallography: probing structural reorganization

X-ray diffraction under laser irradiation


Most of these publications are available on the open archive HAL, in the respect for the policy of the publishers.

103 E. Collet, M. Cammarata
    Concept article: Disentangling ultrafast electronic and structural dynamics with X-ray lasers
    Chemistry: a European Journal, doi 10.1002/chem.201802105 (2018)

102 S. Xue, Y. Guo, A. Rotaru, H. Müller-Bunz, G. G. Morgan, E. Trzop, E. Collet, J. Olah, Y. Garcia
Spin crossover behaviour in a homologous series of iron(II) complexes based on functionalized-bipyridyl ligands
    Inorganic Chemistry, in press (2018)

101 A. Djemel, O. Stefanczyk, M. Marchivie, E. Trzop, E. Collet, C. Desplanches, R. Delimi, G. Chastanet
    Solvatomorphism-Induced 45 K Hysteresis Width in a Spin Crossover Mononuclear Compound
    Chemistry: a European Journal, (2018)

100 K. A. Zenere, S. G. Duyker, E. Trzop, E. Collet, B. Chan, P.W. Doheny, C. J. Kepert and S. M. Neville*
      Increasing spin crossover cooperativity in 2D Hofmann-type materials with guest molecule removal
      Chemical Science, 10.1039/C8SC01040D (2018)

99 O.Jeannin, E. W. Reinheimer, P. Foury-Leylekian, J.-P. Pouget, P. Auban-Senzier, E. Trzop, E. Collet, M. Fourmigue
Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (o-Me2TTF)2NO3
      IUCr Journal 5, 361–372 (2018)

98 S. Zerdane, E. Collet,* X. Dong, S. F. Matar, H. F. Wang, C. Desplanches, G. Chastanet, M. Chollet, J. M. Glownia, H.T. Lemke, M. Lorenc, M. Cammarata,*
Electronic and structural dynamics during the switching of the photomagnetic complex [Fe(L222N5)(CN)2]
      Chemistry A European Journal 24, 5064-5069 (2018)

97 E. Collet, P. Guionneau
Structural analysis of spin-crossover materials: From molecules to materials
      Comptes Rendu Chimie Académie des Sciences doi 10.1016/j.crci.2018.02.003 (2018)

96 S. Zerdane, M. Cammarata,* L. Balducci, R. Bertoni, L. Catala, S. Mazerat, T. Mallah, M. N. Pedersen, M. Wulff, K. Nakagawa, H.Tokoro, S. Ohkoshi, E. Collet,*
      Probing transient photoinduced charge-transfer in Prussian Blue Analogues with time-resolved XANES and optical spectroscopy
      European Journal of Inorganic Chemistry 272-277 (2018)

95  M. Chergui* and E. Collet*
     Photoinduced structural dynamics of molecular systems mapped by time-resolved x-ray methods.
      Thematic Issue 2017 Ultrafast Processes in Chemistry
Chemical Reviews, 117 (16), 11025–11065 (2017)

94  S. Zerdane, L. Wilbraham, M. Cammarata,* O. Iasco, E. Rivière, M.-L. Boillot, I. Ciofini, and E. Collet*
     Comparison of structural dynamics and coherence of d-d and MLCT light-induced spin state trapping
     Chemical Science 8, 4978-4986 (2017)          OPEN ACCESS

93 R.Kulmaczewski, E.Trzop, L.J. Kershaw Cook, E.Collet,*  G.Chastanet*  and  M.A. Halcrow* 
The role of symmetry breaking in the structural trapping of light-induced excited spin states
      Chemical Communication 53, 13268 (2017)

92 H. T. Lemke*, K. S. Kjær, R. Hartsock, T. B. van Driel, M. Chollet, J. M. Glownia, S. Song, D.  Zhu, E. Pace, S. F. Matar, M. M Nielsen, M. Benfatto, K. J. Gaffney, E. Collet, Marco Cammarata*
     Coherent structural trapping through wave packet dispersion during photoinduced spin state switching
       Nature Communication, 8, 15342 (2017)         OPEN ACCESS

91 Y. Jiang, L. Chung Liu, H. M. Müller-Werkmeister, C. Lu, D. Zhang, R. L. Field, A. Sarracini, G. Moriena, E. Collet, R. J. D. Miller*
     Structural Dynamics upon Photoexcitation in a Spin Crossover Crystal probed with Femtosecond Electron Diffraction
     Angewandte Chemie International Edition 56, 7130-7134 (2017)

90 T. Parpiiev, M. Servol, M. Lorenc, I. Chaban, R. Lefort, E. Collet, H. Cailleau, P. Ruello, N. Daro, G. Chastanet, T. Pezeril.
Ultrafast non-thermal laser excitation of gigahertz longitudinal and shear acoustic waves in spin-crossover molecular crystals [Fe(PM-AzA)2(NCS)2      
      Applied Physics Letters (2017)

89 I. Jeon,  C. Mathoniere,  R. Clerac,  M. Rouzieres,  O. Jeannin,  E. Trzop,  E. Collet  and  M. Fourmigue 
    Photoinduced reversible spin-state switching of an FeIII Complex assisted by a halogen-bonded supramolecular network
     Chemical Communications doi 10.1039/C7CC03797J (2017)

88 C. Enachescu*, L. Stoleriu, M. Nishino, S. Miyashita, A. Stancu, M. Lorenc, R. Bertoni, H. Cailleau, E. Collet
      A theoretical approach for elastically driven cooperative switching of spin crossover compounds impacted by an ultrashot laser pulse
      Physical Review B 95, 224107 (2017)

87  M. Buron-Le Cointe, E. Collet, B. Toudic, P. Czarnecki, H. Cailleau*
      Back to the Structural and Dynamical Properties of Neutral-Ionic Phase Transitions
      Crystals 7, 285 (2017).                                                                                      OPEN ACCESS

86  C. Mariette, E. Trzop, S. Zerdane, P. Fertey, D. Zhang, F.J. Valverde-Munoz, J.A. Real, E. Collet*
      Formation of local spin-state concentration waves during the relaxation from photoinduced state in a spin-crossover polymer
      Acta Crystallographica B, in press (2017)

85 Daopeng Zhang, Elzbieta Trzop, Francisco J. Valverde-Muñoz, Lucía Piñeiro-López, M. Carmen Muñoz, Eric Collet,* and José A. Real*
      Competing phases involving spin-state and ligand structural orderings in a multistable two-dimensional spin crossover coordination polymer
       Crystal Growth & Design, 17, 2736-2745 (2017)

84 R. Bertoni, M. Lorenc*, H. Cailleau, A. Tissot, J. Laisney, M.-L. Boillot, L. Stoleriu, A. Stancu, C. Enachescu, E. Collet*.
       Elastically driven cooperative response of a molecular material impacted by a laser pulse
       Nature Materials 15, 606-610 (2016)

83 E. Trzop, D. Zhang, L. Piñeiro-Lopez, F.J. Valverde-Muñoz, M. C. Muñoz, L. Palatinus, L. Guerin, H. Cailleau, J. A. Real and E. Collet*
      First step towards Devil’s Staircase in Spin Crossover materials
       Angewandte Chemie Int. Ed. 55, 8675–8679 (2016)

82 R. Bertoni, M. Lorenc, T. Graber, R. Henning, K. Moffat, J.-F. Létard, and E. Collet*
      Cooperative elastic switching vs laser heating in [Fe(phen)2(NCS)2] spin-crossover crystals excited by a laser pulse

       Cryst.Eng.Comm. 18, 7269-7275 (2016)

81 H. Watanabe, K. Tanaka, N. Bréfuel, H. Cailleau, J.-F. Létard, S. Ravy, P. Fertey, M. Nishino, S. Miyashita, and E. Collet*.
      Ordering phenomena of high-spin/low-spin states in stepwise spin-crossover materials described by the ANNNI model.

       Phys. Rev. B 93 014419 (2016)

80 E. Collet*, L. Henry, L. Piñeiro-López,  L. Toupet and J.A. Real
      Single Laser Shot Spin State Switching of [FeII(Py)Pt(CN)4] Inside Thermal Hysteresis studied by x-ray diffraction
       Current inorganic Chemistry, 6, 61-66 (2016)

79 A. Marino, M. Cammarata, S.F. Matar, J.-F. Létard, G. Chastanet, H. T. Lemke, E. Collet*.
      Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: a molecule-to-lattice energy transfer

       Structural Dynamics 3, 023605 (2016)

78 A. J. Fitzpatrick, E. Trzop, H. Müller-Bunz, M. M. Dîrtu, Y. Garcia, E. Collet* and G. G. Morgan*.
      Electronic vs Structural Ordering in a Manganese(III) Spin Crossover Complex
       Chem Comm. DOI: 10.1039/c5cc05129k (2015)

77 M. Servol, N. Moisan, E. Collet, H. Cailleau, W. Kaszub, L. Toupet, D. Boschetto, T. Ishikawa, A. Moréac, S. Koshihara, M. Maesato, M. Uruichi, X. Shao, Y. Nakano, H. Yamochi, G. Saito, M. Lorenc
      Local response to light excitation in the charge-ordered phase of (EDO-TTF)2SbF6
       Phys. Rev. B 024304 (2015)

76 R. Bertoni, M. Lorenc, J. Laisney, A. Tissot,A. Moréac, S.F. Matar, M. L. Boillot, E. Collet*
      Femtosecond spin-state photo-switching dynamics in an FeIII spin crossover solid accompanied by coherent structural vibrations
        J. Mat. Chem. C 3, 7792-7801 (2015)

75 K. Drużbicki, J. Mielcarek, A. Kiwilsza, L. Toupet, E. Collet, A. Pajzderska, J. Wasicki.
      Computationally Assisted (Solid-State DFT) Structural (X-Ray) and Vibrational Spectroscopy(FT-IR, FT-RS, TDs-THz) Characterization of the Cardiovascular Drug – Lacidipine
       Crystal Growth & Design 15, 2817-2830 (2015)

74 R. Bertoni, M. Cammarata, M. Lorenc, S. Matar, J.F. Létard, H. Lemke, E. Collet*.
      Ultrafast Light-Induced Spin-State Trapping Photophysics Investigated in Fe(phen)2(NCS)2 Spin-Crossover Crystal
       Accounts of Chemical Research 48, 774-781 (2015)

73 A. Marino, M. Buron-Le Cointe*, M. Lorenc, L. Toupet, R. Henning, A.D. DiChiara, K. Moffat, N. Brufel, E. Collet*
      Out-of-equilibrium dynamics of photoexcited spin-state concentration waves
       Faraday Discussion 177, 363-379 (2015).

72 R. Bertoni, M. Lorenc*, A. Tissot, M.-L. Boillot & E. Collet*
      Femtosecond photoswitching dynamics and microsecond thermal conversion driven by laser heating in FeIII spin-crossover solids 

       Coord. Chem. Rev. 282-283 66-76 (2015)
71 M. Cammarata, R. Bertoni, M. Lorenc, H. Cailleau, S. Di Matteo, C. Mauriac, J.F. Létard, S. Matar, H. Lemke, M. Chollet, S. Ravy, C. Laulhé, E. Collet*.
      Sequential activation of molecular breathing and bending during spin-crossover photoswitching revealed with femtosecond optical and x-ray absorption spectroscopy

      Physical Review Letters 113  , 227402 (2014)

70 W. Kaszub, A. Marino, M. Lorenc, E. Collet*, E.G. Bagryanskaya, E.V. Tretyakov, V.I. Ovcharenko, M.V. Fedin

      Ultrafast photoswitching in copper-nitroxide based molecular magnet
       Ang. Chem. Int. Ed 53, 10636 –10640 (2014).

69 A. Marino, P. Chakraborty, M. Servol, M. Lorenc, E. Collet, A. Hauser

      The role of ligand-field states in the ultrafast photophysical cycle of the prototypical iron(II) spin-crossover compound [Fe(ptz)6](BF4)2

      Ang. Chem. Int. Ed 53, 3863-3867(2014).

68 K.D. Murnaghan, C. Carbonera, L. Toupet, M. Griffin, M.M. Ditru, C. Desplanches, Y. Garcia, E. Collet, J.F. Létard, G. Morgan

      Spin state ordering on one Sub-lattice of a Mononuclear Iron(III) Spin Crossover Complex exhibiting LIESST and TIESST
       Chemistry: A European Journal 20, 5613-5618(2014)
67 A. Tissot, E. Rivière, R. Guillot, L. Toupet, M.L. Boillot.

      Light-Induced Excited Spin State Trapping effect on [Fe(mepy)3tren](PF6)2 solvated crystals.

      Dalton Transaction 43, 1063-1071 (2014).

66 F. Camerel, G. Le Helloco, T. Guizouarn, O. Jeannin, M. Fourmigue, A. Frackowiak, I. Olejniczak, R. Swietlik, A. Marino, L. Toupet, E. Collet, P. Auban-Senzier, E. Canadell
"Correlation between Metal–Insulator Transition and Hydrogen-Bonding Network in the Organic Metal δ-(BEDT-TTF)4[2,6-Anthracene-bis(sulfonate)]·(H2O)4"

      Crystal Growth & Design, 13 (11) 5135–5145 (2013)

65 B. Siwick & E. Collet "Molecular motion watched" 
    News & Views   Nature, 496, 306 (2013) 
64 H. Cailleau, M. Lorenc, M. Buron-Le Cointe, M. Servol, M. Cammarata, E.Collet
Impacting materials by light and seeing their structural dynamics
       Eur.Phys.J.SpecialTopics 222, 1077–1092 (2013)

63 A. Marino, M. Servol, R. Bertoni, M. Lorenc, C. Mauriac, J.-F. Létard, E. Collet
Femtosecond optical pump-probe reflectivity studies of spin-state photo-switching in the spincrossover molecular crystals [Fe(PM-AzA)2(NCS)2]
       Polyhedron 66, 123-128 (2013) 
62 A. Tissot, H. J. Shepherd, L. Toupet, E. Collet, J. Sainton, G. Molnár, P. Guionneau, M.-L. Boillot*
Temperature and pressure-induced switching of the molecular spin states of the orthorhombic [(TPA)Fe(TCC)]SbF6 spin-crossover salt.
       Eur. J Inorg. Chem. 5-6, 1001-1008 (2013) 
61 W. Kaszub, M. Buron-Le Cointe, M. Lorenc, M.-L. Boillot, M. Servol, A. Tissot, L. Guérin, H. Cailleau, E. Collet*
Spin-state photoswitching dynamics of the [(TPA)Fe(TCC)]SbF6 complex
       Eur. J Inorg. Chem 5-6, 992-1000 (2013)

60 H. Watanabe, N. Bréfuel, E. Collet, L. Toupet, K. Tanaka, J.-P. Tuchagues*
Symmetry breaking versus spin crossover during the thermal pathway and the out-of-equilibrium relaxation dynamics in the [FeH2L2-Me](ClO4)2 complex
       Eur. J Inorg. Chem. 5-6, 710-715 (2013) 
59 E. Collet, H. Watanabe, N. Bréfuel, L. Palatinus, L. Roudaut, L. Toupet, K. Tanaka, J.-P. Tuchagues, P. Fertey, S. Ravy, B. Toudic, H. CailleauAperiodic spin state ordering of bi-stable molecules and its photoinduced erasing
Phys. Rev. Lett. 109, 257206 (2012)
58  P. Czarnecki, A. Pajzderska, E. Collet, L. Toupet, J. Wasicki,
            "New Ferroelectric: Bis-Thiourea Pyridinium Bromide Inclusion Compound"
Journal of Materials Research, 27 2844-2850 (2012).
57 R. Bertoni, M. Lorenc*, A. Tissot, M. Servol, M.-L. Boillot & E. Collet*
            “Femtosecond spin-state photo-switching of molecular nanocrystals evidenced by optical spectroscopy”
            Ang. Chem. Int. Ed 51, 7485 –7489 (2012).
56 E. Collet*, M. Lorenc, M. Cammarata, L. Guérin, M. Servol, A. Tissot, M.L. Boillot,H. Cailleau, M. Buron
    "100 picosecond diffraction catches structural transients of laser-pulse triggered switching in a spin-crossover

             Chemistry: A European Journal 18, 2051-2055 (2012)
55 E. Collet*, N. Moisan, C. Baldé, R. Bertoni, E. Trzop, C. Laulhé, M. Lorenc, M. Servol, H. Cailleau, A. Tissot, M.L. Boillot, T. Graber, R. Henning, P. Coppens and M. Buron  

“Ultrafast spin-state photoswitching in a crystal and slower consecutive processes investigated by femtosecond optical spectroscopy and picosecond X-ray diffraction"
             Phys. Chem. Chem. Phys. 14, 6192-6199 (2012)
54 M. Buron-Le Cointe, J. Hébert, C. Baldé, N. Moisan1, L. Toupet, P. Guionneau, J.F. Létard, E. Freysz, H. Cailleau, E. Collet*   

" Intermolecular control of thermo- and photo-switching phenomena in two spin-crossover polymorphs "
             Phys. Rev. B. 85, 85, 064114 (2012)
53 M. Lorenc, Ch. Balde, W. Kaszub, A. Tissot, N. Moisan, M. Servol, M. Buron-Le Cointe, H. Cailleau, P. Chasle, P. Czarnecki, M. L. Boillot, E. Collet
"Cascading photo-, elasto- and thermo-switching of spin-state triggered by a femtosecond laser pulse in an Fe(III) molecular crystal"
             Phys. Rev. B. 85, 054302 (2012)
52 C. D’Amico, M. Lorenc, E. Collet, K. Green, K. Costuas, O. Mongin, M. Blanchard-Desce, and F. Paul*,
" Probing Charge Transfer Excited States in a Quasi Non-Luminescent Electron-Rich Fe(II)-Acetylide Complex by Femtosecond Optical Spectroscopy"
             Journal of Physical Chemistry C116, 3719-3727 (2012)
51 H. Cailleau, T. Luty, S. Koshihara, M. Servol, M. Lorenc, M. Buron-Le Cointe,E. Collet.
         “PIPT from the Beginning to Future” Acta Physica Polonica A, 121, 297-306 (2012)

50 Y. Okimoto, T. Miyata, M.S. Endo, M. Kurashima, K. Onda, T. Ishikawa, S. Koshihara, M. Lorenc, E. Collet, H. Cailleau, and T. Arima

"Ultrafast spectral weight transfer in RBaCo2O6δ (R=Sm, Gd, and Tb): A role of electronic correlation in photoinduced phase transition"
            Physical Review B, 84, 121102 (2011)
49 A. Tissot, R. Bertoni, E. Collet, L. Toupet, M.L. Boillot

"The cooperative spin-state transition of an iron(III) compound [FeIII(3-MeO-SalEen)2]PF6: thermal- vs ultra-fast photo-switching".
             Journal of Materials Chemistry, 35, 2333-2340 (2011)
48 H. Watanabe, H. Hirori, S. Mouri, N. Bréfuel, J.P. Tuchagues, E. Collet, K. Tanaka
Dynamical separation of the coupled order parameters in the relaxation process from the photo-induced state"

             Europhysics Letters, 96 17004 (2011).
47 C. Laulhé, S. Ravy, P. Fertey, E. Elkaim, F. Legrand, P. Féret, Ph. Hollander, S. Hustache, M. Bordessoule, J.-P. Ricaud, E. Collet, M. Lorenc, M. Buron- Le Cointe, H. Cailleau, A. Tissot, M.-L. Boillot
"Time-resolved pump-probe diffraction experiment at SOLEIL synchrotron: photoinduced spin transition in the molecular crystal [TPA Fe(III) TCC] PF6".
            Submit. to Acta Physica Polinica A, special issue.
46 W. Kaszub, E. Collet, H. Cailleau, M. Servol, M-L. Boillot, A. Tissot, M. Lorenc

" White light snapshot of non-equilibrium high spin state in a molecular crystal "
            Acta Physica Polinica A, special issue, in press.
45 F. Varret, A. Slimani, K. Boukheddaden, C. Chong, H. Mishra, E. Collet, J. Haasnoot, S. Pillet
"The propagation of the thermal spin transition of Fe(btr)2(NCS) 2].H2O single crystals, observed by optical microscopy."

             New journal of Chemistry, 35, 2333–2340 (2011)
44 O.J. Hernandez, C. Tassel, K. Nakano, W. Paulus, C. Ritter, E. Collet, A. Kitada, K. Yoshimurac, H. Kageyama

"First single-crystal synthesis and low temperature structural determination of the quasi-2D quantum spin compound (CuCl)LaNb2O7"
             Dalton Transactions, 40 4605-4613 (2011).
43 C. Chong, F. Varret,K. Boukheddaden, E. Collet, J.C. Ameline, R. Bronisz, A. Hauser
"The stepwise temporal evolution of the thermal spin transition in [Fe(bbtr)3](ClO4)2 single crystals explained by optical microscopy in terms of inhomogeneous stresses".
            Chem. Phys. Lett. 504 29-33 (2011)
42 L. Guérin, J. Hébert, M. Buron-Le Cointe, S. Adachi, S. Koshihara, H. Cailleau, Eric Collet*.
    "Capturing one-dimensional precursors of a photoinduced transformation in a material",
            Phys. Rev. Lett.105, 246101 (2010).
41 C. Tassel,J. Kang,C. Lee,O. Hernandez,Y. Qiu,W. Paulus,E. Collet,B. Lake,T. Guidi,M.-H. Whangbo,C. Ritter,H. Kageyama,and S.-H. Lee*

"Ferromagnetically coupled Shastry-Sutherland quantum spin singlets in (CuCl)LaNb2O7",
            Phys. Rev. Lett.105, 167205 (2010).
40 E. Collet "Dynamical structural science"
            Acta Cryst. A. 66, 133-134 (2010).
39 N. Bréfuel, E. Collet*,  H. Watanabe, M. Kojima, N. Matsumoto, L. Toupet, K. Tanaka, J.P. Tuchagues*

"Nanoscale self-hosting of molecular spin states in the intermediate phase of spin-crossover materials"
            Chem. Eur. J. 16 14060-14068 (2010).
38 H. Svendsen, J. Overgaard, M. Chevallier, E. Collet, Y. Chen, F. Jensen, B.B. Iversen*,
"Photomagnetic switching of heterometallic complexes, M1(DMF)4(H2O)3(µ-CN)Fe(CN)5H2O, M1 = Nd, La, Gd, Y, analyzed by single crystal X-ray diffraction and ab initio theory"
            Chem. Eur. J. 16, 7215-7226 (2010).
37 C. Chong, H. Mishra, K. Boukheddaden, S. Denise, G. Bouchez, E. Collet, J.C. Ameiline,A. Naik, Y. Garcia, F. Varret*,

" Electronic and Structural Aspects of Spin Transitions observed by Optical Microscopy. The case of [Fe(ptz)6](BF4)2"
            J. Phys. Chem. B 114, 1975-1984 (2010).
36 H. Cailleau, M. Lorenc, L. Guérin, M. Servol, E. Collet, M. Buron-Le Cointe
"Structural dynamics of photoinduced molecular switching in the solid state"

            Acta Cryst. A. 66, 189-197 (2010).
35 N. Bréfuel*, H. Watanabe, L. Toupet, J. Come, M. Kojima, N. Matsumoto, E. Collet*
K. Tanaka, J.P. Tuchagues* "Concerted Spin Crossover and Symmetry Breaking Yield three Thermally- and one Light-Induced Crystallographic Phases of a Novel Molecular Material"

            Ang. Chem. Int. Ed 48, 9304-9307 (2009).
34 M. Lorenc, J. Hébert, N. Moisan, E. Trzop, M. Servol, M., Buron,H. Cailleau, M.L. Boillot, E. Ponte, M. Wulff, S. Koshihara, E. Collet*        

"Successive dynamical steps of photoinduced switching of a molecular Fe(III) spin-crossover material by time-resolved x-ray diffraction",
            Phys. Rev. Lett. 103, 028301 (2009).
33 T. Ishikawa, N. Fukazawa,Y. Matsubara, R. Nakajima, K. Onda, Y. Okimoto, S. Koshihara, M. Lorenc,E. Collet, M. Tamura* and R. Kato

Large and ultrafast photoinduced reflectivity change in the charge separated phase of in Et2Me2Sb[Pd(dmit)2]2
            Physical Review B 80, 115108 (2009).
32 . E. Collet,* M.L. Boillot, J. Hebert, N.Moisan, M. Servol, M. Lorenc, L. Toupet, M. Buron-Le Cointe, A. Tissot, J. Sainton

" Polymorphism in the spin-crossover ferric complex [(TPA)Fe(III)(TCC)] PF6",
            Acta Cryst. B 65, 474-480 (2009).
31 H. Svendsen, J. Overgaard, M. Chevallier, E. Collet, B.B. Iversen*
       "Single crystal X-ray diffraction study of the excited state structure of photo-magnetic complex, Nd(DMF)4(H2O)3(µ-CN)Fe(CN)5∙ H2O "
            Ang. Chem. Int. Ed. 48, 2780-2783(2009).
30 A.  Pajzderska*, E. Collet, P. Czarnecki, J. Wąsicki
" Ferroelectricity of inclusion compounds of thiourea with pyridinium iodide and nitrate "
            J. Phys. Chem. C 113, 6282-6289(2009).
29 A.  Pajzderska*, J. Wąsicki, P. Czarnecki, L. Toupet, E. Collet
"Discovery of an intermediate phase in bis-thiourea pyridinium chloride inclusion compound "
            J. Chem. Phys. 130, 044503. (2009).
28 T.Ishikawa*, N. Fukazawa, Y. Matsubara, R. Nakajima, K. Onda, Y. Okimoto, S. Koshihara, M. Tamura, R. Kato, M. Lorenc, E. Collet

"The photo-induced phase transition in Et2Me2Sb[Pd(dmit)2]2"
            Phys. Stat. Sol.(c) 1,112-115 (2009).
27 B. Toudic*, P. Garcia, C. Odin, P. Rabiller, C. Ecolivet, E. Collet, P. Bourges, G.J. Mc Intyre, M.D. Hollingsworth, T. Breczewski.
    "Hidden degrees of freedom in aperiodic materials"
            Science 316, 69-71 (2008).
26 D. Glijer, J. Hebert, E. Trzop, E. Collet, L. Toupet, H. Cailleau, , G.S. Matouzenko, H.Z. Lazar J.-F. Létard, S. Koshihara, M. Buron-Le Cointe*.

"Photoinduced phenomena and structural analysis associated with the spin state switching in the [Fe(DPEA)(NCS)2] complex"
            Physical Review B, 78,134112 (2008).
25 A.  Pajzderska*, J. Wąsicki, H. Małuszyńska, P. Czarnecki, L. Toupet, E. Collet
"Structural and dynamical aspects of the phase transition in the new thiourea thiazolium Br inclusion compound"
            J. Chem. Phys., 129, 104501 (2008).
24N. Moisan, M. Servol, M. Lorenc, A. Tissot, M.L. Boillot, H. Cailleau, S. Koshihara, E. Collet*            
"Towards ultrafast photoinduced spin state switching in molecular solids",
            Comptes Rendus Chime Académie des Sciences 11, 1235-1240 (2008).
23 Eric Collet*, Maciej Lorenc, Marylise Buron, Hervé Cailleau
  " State of the art and opportunities in probing photoinduced phase transitions in molecular materials by conventional and picosecond X-ray diffraction".
            Zeitschrift fuer Kristallographie 223, 272-282 (2008).
22 V. Mishra, R. Mukherjee, J. Linares, François Varret, J. F. Létard, E. Collet, M.Castro

“Narrow hysteresis and spin transition properties of [FeII(L6)2][ClO4]2.C7H8 investigated by magnetic, structural, calorimetric and spectroscopic means”
            Inorg. Chem 47, 7577-7587 (2008).
21 A. Goujon, F. Varret*, K. Boukheddaden, C. Chong, J Jeftic, Y. Garcia, A. D. Naik, J.C. Amelineand E. Collet
"An optical microscope study of photo-switching and relaxation in single crystals of the spin transition solid [Fe(ptz)6](BF4)2, with image processing"
            Inorganica Chimica Acta, 361, 4055-4064 (2008).
20 S. Nozawa*, S. Adachi,J. Takahashi, R. Tazaki, L. Guérin, M. Daimon,A. Tomita,T. Sato, M. Chollet, E. Collet, H. Cailleau, S. Yamamoto, K. Tsuchiya, T. Shioya, H. Sasaki, T. Mori, K. Ichiyanagi, H. Sawa, H. Kawatab and S. Koshihara.
     "Developing 100-picosecond resolved X-ray structural analysis capabilities at the NW14A, Photon Factory Advanced Ring"
            Journal of Synchrotron Radiation 14, 313–319 (2007).
19 M.H. Lemée-Cailleau*, E. Collet, M. Buron-Le Cointe, N. Grach, B. Ouladdiaf, F. Moussa, T. Hasegawa, Y. Takahashi, T. Roisnel, H. Cailleau
"Down to the quantum limit at the Neutral-to-Ionic phase transition of
    (BEDT-TTF)-(ClMe-TCNQ) – Symmetry analysis and phase diagram"

            J. Phys. Chem. B, 111 (22), 6167-6172 (2007).
18 N. Ould Moussa, E. Trzop, S. Zein, G. Molnar, E. Collet*, M. Buron, J.A. Real*, S. Borshch, K. Tanaka, H. Cailleau, A. Bousseksou*,          

"Wavelength Selective Photomagnetic Phenomena in the Dinuclear Spin
    Crossover Compound {[Fe(bt)(NCS)2]2(bpym)}
            Physical Review B, 75 054101(2007).
17 E. Trzop, M. Buron-Le Cointe,H. Cailleau,L. Toupet, G. Molnar,A. Bousseksou, A. B.Gaspar,J. A. Real*andE.Collet*   

"Structural Investigation of the Photoinduced Spin Conversion in the Binuclear Compound {[Fe(bt)(NCS)2](bpm)}:Toward Multi-stepped Molecular Switches.",
            Journal of Applied Crystallography 40, 158-164 (2007).
16 M. Buron-Le Cointe, MH Lemée-Cailleau, H. Cailleau, S. Ravy, JF Bérar, S. Rouzière, E. Elkaim, E. Collet
    "1D Fluctuating Nanodomains in the C-T Molecular System TTF-CA and their First-Order Crystallization"
            Physical Review Letters, 96 205503 (2006).
15K. Ichiyanagi*, J. Hebert, L. Toupet, H. Cailleau, E. Collet*, P. Guionneau, J.F. Létard,
   "Structural investigation of the photoinduced spin transition in the [Fe(PM-BiA)2(NCS)2] compound".
Solid State Phenomena, 112, 81-88(2006).
14K. Ichiyanagi, J. Hebert, L. Toupet, H. Cailleau, P. Guionneau, J.F. Létard, E. Collet*.
     "Cooperative photoinduced spin transition in [Fe(PM-BiA)2(NCS)2] driven by a domain nucleation process".
Rapid communication, Physical Review B, 73 060408(R) (2006).
13 E. Collet*, M. Buron-Le Cointe, H. Cailleau
      "Photoinduced structural transition probed by time-resolved X-ray in electron-lattice and electron-spin
       interacting system".
Journal of the Physical Society of Japan, 75(1), 011002 (2006).
12 M. Buron-Le Cointe*, E. Collet, L. Guérin, M.H. Lemée-Cailleau, H. Cailleau, M. Wulff, T. Luty, S. Koshihara, K. Tanaka,
     "Time-resolved X-ray diffraction: a wonderful tool for probing structural photoinduced phase transitions.",
Journal of Luminescence: 112/1-4, 235 (2005).
11 S. Adachi*, H. Kawata, S. Koshihara, M. Daimon, H. Cailleau, E. Collet
    "Pump-probe X-ray crystallography with 100 picosecond X-ray pulse and femtosecond laser".
OYO BUTURI, Japanese journal of Applied Physics, 73(6), 725-731 (2004).
10N. Huby, L. Guérin, E.Collet*, L. Toupet, J.C. Ameline, H. Cailleau, T. Roisnel, T. Tayagaki, K. Tanaka
    " Photoinduced Spin Transition Probed by X-ray Diffraction"
            Rapid communication, Physical Review B69 020101(R) (2004).
9 L. Guérin*, E. Collet*, M.H. Lemée-Cailleau, M. Buron, H. Cailleau, A. Plech, M. Wulff, S. Koshihara, T. Luty
   "Probing photoinduced phase transition in a charge-transfer crystal by 100 picosecond X-ray diffraction"
Chemical Physics, 299 163 (2004).
8 E. Collet*, M.H. Lemée-Cailleau, M. Buron-Le Cointe, H. Cailleau, M. Wulff, T. Luty, S. Koshihara, M. Meyer, L. Toupet, P. Rabiller, S. Techert
   "Laser-induced ferroelectric structural order in an organic charge-transfer crystal"
            Science, 300, 612-615 (2003).
7 T. Luty*, T. Ogawa, Y. Okajima, E. Zienkiewicz, H. Cailleau, S. Koshihara, E. Collet, M. Buron-Le Cointe, M.H. Lemée-Cailleau,
          "Photoinduced transformations : three-state model",
                        Phase transition, 75 659-671 (2002).
6 T. Luty*, H. Cailleau  , S. Koshihara, E. Collet, M. Takesada,   M.H. Lemée-Cailleau, M. Buron-Le Cointe, N. Nagaosa, Y. Tokura, E. Zienkiewicz, B. Ouladdiaf,
   "Static and dynamic order of cooperative multielectron transfer",
Europhysics Letters, 59(4), 619-625 (2002).
5 E. Collet*, M.H. Lemée-Cailleau, M. Buron, H. Cailleau, S. Ravy, T. Luty, J.F. Bérar, P. Czarnecki, N. Karl,
  "Direct evidence of lattice-relaxed charge-transfer exciton-strings",
Europhysics Letters, 57(1) 67-73 (2002).
4 H. Cailleau*, T. Luty, M.H. Lemée-Cailleau, E. Collet, M. Buron-Le Cointe, E. Zienkiewicz, F. Moussa,
  "Pressure tuning of condensation and ordering of charge-transfer strings",
NATO Science Series II: Mathematics, Physics & Chemistry, 167-178 (2001).
3 E. Collet*, M. Buron-Lecointe, M.H. Lemée-Cailleau, H. Cailleau, L. Toupet, M. Meven, S. Mattauch, G. Heger, N. Karl,

"Structural evidence of ferrielectric neutral-ionic layered ordering in DMTTF – p-chloranil",
Physical Review B, 63(1), 1-12 (2001).
2 H. Cailleau*, E. Collet, T. Luty, M.H. Lemée-Cailleau, M. Buron-Le Cointe, S. Koshihara
  "Cooperativity at neutral-ionic transformation",
NATO Science Series, 3-79 High Technology, 451-465 (2000).
1 M.H. Lemée-Cailleau*, M. Buron-Le Cointe, E. Collet, H. Cailleau , T. Luty
"Singular solid-liquid-gas like phase diagram of neutral-to-ionic transition"
            NATO ASI Science Series, E 358, 219-224 (1999)

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We use ultra-short laser for switching physical properties of materials. Let’s play with matches and look at what happens when one shine them with laser of continuous or pulsed nature.

Playing with matches