SPECTROSCOPIC CONSTANTS AND POTENTIAL-ENERGY CURVES OF IRH

Complete active space multi-configuration self-consistent field (CASMCSCF) followed by first-order configuration interaction (FOCl) and multireference singles + doubles Cl (MRSDCl) calculations are made on 19 low-lying electronic states of IrH. We also carry out relativistic Cl(RCl) calculations including spin-orbit coupling to compute spin-orbit effects on the low-lying states of IrH. The potential energy curves of low-lying electronic states of IrH are computed. The ground state of IrH is found to be an intermediate-coupled (3)SIGMA- + (3)PI) admixture with 0+ symmetry. Several spectroscopic transitions for the diatomic iridium hydride are predicted none of which has been observed experimentally. The Mulliken population analyses of the (3)SIGMA- and (3)PI states of IrH reveal that the Ir atom is an effective configuration of 6s(1.59)6p(0.10)5d7.28 and 6s(1.48)6p(0.08)5d7.4 in these states, respectively exhibiting Ir+H- polarity. The 0+ ground state of IrH is found to be a 43% (3)SIGMA-, 29% (3)PI and 12% (1)SIGMA+ mixture near its equilibrium geometry. The spectroscopic properties of IrH are also compared with RhH.