Table of Contents
Laser Chemistry
Volume 19, Issue 1-4, Pages 45-49

Vibrational Cooling After Photo Isomerisation: First Application of a Novel Intramolecular Thermometer

1Institut für Medizinische Optik, Ludwig Mximilians Universität München, Barbarastr. 16, München 80797, Germany
2Department of Chemistry, University of Pennsylvania, Philadelphia 19104, PA, USA
3Department of Chemistry, Wellesley College, Wellesley 02181, MA, USA

Received 7 April 1997

Copyright © 1999 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Femtosecond VIS-pump-IR-probe experiments (time resolution: 300fs, detectable absorption change: 5.10-5 , frequency range: 1000–1800 cm-1) were applied to the ultrafast photo isomerisation of azobenzene and the protonated Schiff base of retinal. The energy of the pump photon heats the vibrational system of the molecule, leading to pronounced anharmonic frequency shifts which are dominated by the anharmonic coupling between the investigated high frequency modes to hot low frequency modes. A model taking into account this intramolecular anharmonicity and assuming a well defined intramolecular temperature gives a good fit of the experimental data.