HIGH-RESOLUTION ABSORPTION, EXCITATION, AND MICROWAVE-UV DOUBLE-RESONANCE SPECTROSCOPY ON A MOLECULAR-BEAM - S-1 ANILINE

A high-resolution, molecular beam UV spectrometer was constructed that uses both traditional laser induced fluorescence and optothermal dete ction of the energy content of the molecular beam. Microwave-UV double resonance capabilities were implemented to assist in the assignment o f the UV spectra of medium-sized molecules with the ultimate goal to u nravel their S-1/T-1 dynamics. It is shown that high quality optotherm al spectra can be obtained in the 300 nm region, by recording the high -resolution, optothermally detected, S-1 <-- S-0 0-0 absorption spectr um of aniline with a signal-to-noise ratio comparable to that of the L IF spectrum of the same band. The latter is used to obtain accurate ro tational constants for the vibrationless S-1 state of this molecule. D ouble resonance is demonstrated by confirming several rotational assig nments in this way.