Time-Resolved Molecular Dynamics

Abstract

Time-resolved experiments have been performed on a diversity of molecular systems. Applications of spectroscopic techniques which work in the time-domain range from the detection of simple vibrational motion of a diatomic molecule to the direct determination of relaxation times in polyatomic molecules in a liquid environment, or the recording of isomerization processes in biomolecules. The underlying principles of these experiments are more or less the same. In this chapter, a brief description of the basic ideas of transient spectroscopy is given with the emphasis on gas-phase molecules under collision-free conditions, as are usually provided in a molecular beam. For the development of ultrashort pulse techniques and their application to areas as different as optical engineering, solid state physics or biology see the series of conference proceedings in [35.1,2,3,4,5,6,7,8,9,10,11,12,13,14]. For special applications to molecular physics and chemistry consult [35.15,16,17,18,19,20,21,22] and the review in [35.23]. Besides an overall rotation and the translational motion of the molecular center of mass, nuclei within a molecule possess vibrational degrees of freedom. The real-time detection of internal vibrational dynamics is discussed in what follows, but the considerations apply equally well to the case of a fragmentation process where the dissociation dynamics is resolved.