Sequential Activation of Molecular Breathing and Bending during Spin-Crossover Photoswitching Revealed by Femtosecond Optical and X-Ray Absorption Spectroscopy

Marco Cammarata (1) , Roman Bertoni (1) , Maciej Lorenc (1) , Hervé Cailleau (1) , Sergio Di Matteo (1) , Cindy Mauriac (2) , Samir Matar (2) , Henrik Lemke (3) , Matthieu Chollet (3) , Sylvain Ravy (4) , Claire Laulhé (4) , Jean-François Létard (2) , Eric Collet (1)

1 IPR - Institut de Physique de Rennes
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 SLAC - SLAC National Accelerator Laboratory
4 SSOLEIL - Synchrotron SOLEIL

We study the basic mechanisms allowing light to photoswitch at molecular scale a spin-crossover material from low-to high-spin state. Combined femtosecond x-ray absorption performed at LCLS X-FEL and optical spectroscopy reveal that the structural stabilization of the photoinduced HS state results from a two step structural trapping. Molecular breathing vibrations are first activated and rapidly damped as part of the energy is sequentially transferred to molecular bending vibrations. During the photoswitching, the system follows a curved trajectory on the potential energy surface.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Physique Quantique [quant-ph]; Chimie de coordination; Matériaux

Marco Cammarata, Roman Bertoni, Maciej Lorenc, Hervé Cailleau, Sergio Di Matteo, et al.. Sequential Activation of Molecular Breathing and Bending during Spin-Crossover Photoswitching Revealed by Femtosecond Optical and X-Ray Absorption Spectroscopy. Physical Review Letters, 2014, 113 (22), pp.227402. ⟨10.1103/PhysRevLett.113.227402⟩. ⟨hal-01088100⟩