FAR INFRARED DIFFERENCE FREQUENCY SPECTROSCOPY OF THE WEAK BOND IN ARHBR

A new tunable far infrared difference frequency spectrometer has been used to observe the Q branch of the lowest Π bending vibration of ArH79Br and ArH81Br. The vibrational frequencies are 26.665635(4) and 26.665284(4) cm-1 for the 79Br and 81Br species respectively. The average center-of-mass separation is 0.07 Å shorter in the excited state than in the ground state and analysis of the bromine nuclear hyperfine structure provides the excited state angular expectation value 〈P2(cosθ)〉 = -0.098(2). The data indicate significant coupling between the bending and stretching coordinates of the complex at angles sampled by the Π state. The results are compared with the best available theoretical calculations for this species and the agreement is found to be excellent. © 1990.