SPECTROSCOPY OF THE INDIUM ARGON VAN-DER-WAALS COMPLEX - A HIGH-RESOLUTION STUDY OF THE B(2)SIGMA(1 2)[-X2(2)PI(3/2) SYSTEM/

The InAr van der Waals complex has been characterized by high resoluti on laser induced fluorescence excitation spectroscopy. Six vibronic ba nds of the B 2SIGMA1/2 <-- X2 2PI3/2 transition have been observed and five of these (v',0), where v' = 1-5, have been rotationally analyzed . Rydberg-Klein-Rees potential curves were constructed for the B 2SIGM A1/2 state using the rotational and vibrational constants determined f rom these spectra. Equilibrium bond lengths were determined for the B and X2 states and a dissociation energy was determined for the B state . The stronger bonding present in the B state is rationalized in terms of penetration of the argon atom into the diffuse 6s orbital of indiu m. Evidence is presented that the B state potential energy curve has a barrier at long range, due to Pauli repulsion, of approximately 60 cm -1. An analysis of the hyperfine structure involving the In-115 nucleu s was made. It is concluded that the X2 state conforms to Hund's coupl ing case alpha(beta), whereas the B state conforms to case b(betas). T he extent of 6s-6p hybridization in the upper state was measured from hyperfine splittings and was used in conjunction with a simple electro static model to estimate the polarizability of the indium atom in the 6S S-2(1/2) state. A value of 68(4) angstrom3 was obtained (1sigma err or).