ULTRA HIGH-RESOLUTION ELECTRONIC SPECTROSCOPY IN MOLECULAR BEAMS. THE $S_{1}\leftarrow S_{0}$ TRANSITION OF 1-FLUORONAPHTHALENE

$^{\ast}$ Work supported by NSF, WPATC, and the University of Pittsburgh.Author Institution: Department of Chemistry, University of PittsburghThe past few years have witnessed major advances in the resolution of spectroscopic experiments carried out in UV, visible, and infrared regions of the electromagnetic spectrum. In this report, we describe the first test of our new laser spectrograph, consisting of a tunable, single-frequency dye laser operating in the UV. a molecular beam machine, and a sophisticated data acquisition system. Linewidths of less than 5 MHz have been achieved in the $S_{1}\leftarrow S_{0}$ fluorescence excitation spectrum or 1-fluoronaphthalene, at ca 310 nm, permitting tests of the instrumental bandwidth and sensitivity as well as a determination of the beam rotational temperature and velocity distribution. Complete resolution of the rotational structure in different vibronic bands also makes possible measurements of the inertial constants of both $S_{1}$ and $S_{0}$ states and the orientation of the optical transition moment relative to the inertial frame. Future applications of this instrument to problems in chemical dynamics will be discussed