This research, part of the Experimental Physical Chemistry Program, involves the development of several new techniques for the observation and assignment of rotation vibration transitions of polyatomic species in excited vibrational levels of the ground electronic state. Pulsed infrared laser excitation is synchronized with the measurements taken to record a Fourier transform infrared spectrum of the polyatomic species in selected excited ro-vibrational states. There are several advantages to this methodology. It simplifies the observed spectrum, thereby facilitating its interpretation. It is also possible to study states that are normally forbidden by one-photon selection rules. In addition it is also possible to study the time evolution of the spectrum. This study will mainly be concerned with the simplification of the infrared spectrum. The research will elucidate the new experimental methodology through the study of symmetric top molecules. The practical extent of the spectral simplification will be determined. Information on excited vibrational states and harmonic vibrational potential constants will be obtained for the species studied. The vibrational energy levels of selected prototypical species involved in multiphoton induced chemistry will be elucidated.
