HYPERFINE-STRUCTURE ANALYSIS OF STIBINE IN THE GROUND AND IN THE UPSILON-4 = 1 STATES

The two isotopic forms of stibine, 121SbH3 and 123SbH3, have been spectroscopically studied with high resolution. Pure quadrupole resonances both in the ground and in the v4 = 1 states have been observed using the infrared-radiofrequency double resonance technique in a CO2 laser cavity. Characteristic hyperfine patterns resulting from direct l-type doubling transitions in the v4 = 1 state have been measured by microwave spectroscopy. The hyperfine pattern in the ground state is reproduced following the standard treatment. Strong vibration-rotation interactions between the v2 = 1 and v4 = 1 states affect the observed spectrum in the v4 = 1 state. A refined treatment of the vibration-rotation interactions between the hyperfine levels in this state was necessary in order to adequately analyze the experimental data. Quadrupole interaction parameters for a degenerate state of a symmetric-top molecule have been determined for the first time. © 1992.