The Spectroscopy of the Formyl Radical.

Fluorescence-excitation and stimulated emission pumping (SEP) spectroscopies were used to study the properties of photolytically generated, gas phase, formyl radical (HCO). This work focused on the ground doublet electronic state, between 4000-11 200cm^{-1} of energy, and the second excited doublet electronic state, between 38 590-38 750cm^{-1 } of energy. From the fluorescence-excitation spectrum the rotational, centrifugal distortion, and spin -rotational constants were determined for the vibrationless level of the second excited doublet electronic state. From the stimulated emission pumping spectrum vibrational term values, rotational constants, spin-rotational constants, and rotational linewidths were determined for ground electronic state vibrational levels--both above and below the dissociation limit for formyl radical dissociating to hydrogen atom and carbon monoxide. The systematics of the dissociation lifetimes, inferred from the observed rotational linewidths, for rovibrational levels of the ground electronic state were studied. The dissociating lifetimes were found to be strongly correlated with bending vibrational excitation and the amount of angular momentum about the minimum inertial axis of formyl radical. The observed dissociation lifetimes indicates the need for an upward adjustment of the currently accepted dissociation limit and barrier height. (Copies available exclusively from MIT Libraries, Rm. 14-0951, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).