Polarization-Detected Transient Gain Studies of Relaxation Processes in V (sub 4) = 1A(2) Formaldehyde-H (sub 2)

摘要

The past two decades have witnessed a rapid growth in the study of electronically excited molecules brought about by the concurrent development of powerful new experimental and theoretical techniques. The formaldehyde molecule, the smallest neutral polyatomic containing the chemically significant carbonyl chromophore, has been the focus of many landmark advances in our conceptual understanding of photochemical and photophysical processes. The present work has employed a form of optical optical double resonance (OODR) in which a cw, single frequency laser serves as an eigenstate-specific probe of molecular relaxation processes. Application of this novel time-resolved technique to formaldehyde-H(sub 2) has enabled us to perform kinetic studies on the A state with sensitivity and resolution which far exceed that attainable by more conventional methods. In particular, our results provide direct evidence that the anomalous nonlinear Stern-Volmer behavior previously observed for individual S1 rovibronic eigenstates is really an experimental artifact arising from detection of undispersed molecular fluorescence. Formaldehyde, reprints. (mgm)