Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: A molecule-to-lattice energy transfer

A Marino; M Cammarata; S F Matar; J-F Létard; G Chastanet; M Chollet; J M Glownia; H T Lemke; E Collet

doi:10.1063/1.4936290

Activation of coherent lattice phonon following ultrafast molecular spin-state photo-switching: A molecule-to-lattice energy transfer

Struct Dyn. 2015 Nov 20;3(2):023605. doi: 10.1063/1.4936290. eCollection 2016 Mar.

Authors

A Marino¹, M Cammarata¹, S F Matar², J-F Létard², G Chastanet², M Chollet³, J M Glownia³, H T Lemke³, E Collet¹

Affiliations

¹ Institute de Physique de Rennes , UMR 6251 University Rennes 1-CNRS, 35042 Rennes, France.
² CNRS, Université de Bordeaux , ICMCB, 87 avenue du Dr. A. Schweitzer, Pessac 33608, France.
³ LCLS, SLAC National Laboratory , Menlo Park, California 94025, USA.

Abstract

We combine ultrafast optical spectroscopy with femtosecond X-ray absorption to study the photo-switching dynamics of the [Fe(PM-AzA)2(NCS)2] spin-crossover molecular solid. The light-induced excited spin-state trapping process switches the molecules from low spin to high spin (HS) states on the sub-picosecond timescale. The change of the electronic state (<50 fs) induces a structural reorganization of the molecule within 160 fs. This transformation is accompanied by coherent molecular vibrations in the HS potential and especially a rapidly damped Fe-ligand breathing mode. The time-resolved studies evidence a delayed activation of coherent optical phonons of the lattice surrounding the photoexcited molecules.