Vibrational overtone driven atmospheric chemistry in isolated molecules and molecular clusters.

Abstract:
In the proposed project we will study photochemical processes relevant for the lower atmosphere chemistry initiated by vibrational excitation of chromophore molecules. Such processes utilize solar radiation in the visible and near IR spectral regions and gain importance when the traditional UV-initiated processes are inefficient. We will perform model laboratory experiments to determine the role of such processes in the Earth troposphere utilizing molecular and cluster beams and unique laser equipment vailable in our laboratory such as the NIR highresolution diode laser spectrometer, the widely tunable pulsed IR OPO laser, as well as tunable UV laser systems for spectroscopy and photodissociation experiments in the near IR and visible spectral regions. The proposed experiments will include the vibrational overtone spectroscopy of atmospherically relevant molecules - both free and in rare-gas and water clusters - using sensitive laser absorption techniques and to study photochemical processes initiated by those excitations with the IR-UV double resonance technique.

Goals:
Experimentally determine the role of vibrational-overtone initiated processes in several model systems that represent important atmospheric species such as acids or alcohols and their derivatives. Obtain overtone spectra in gas phase and in molecular clusters, and determine photochemical pathways.