Laser and Fourier Transform Spectroscopy of PtH and PtD

Abstract

Three new bands of PtH and three new bands of PtD have been rotationally analyzed using laser excitation and Fourier transform spectroscopy. For both PtH and PtD. every band so far identified by laser spectroscopy originates from an Ω = 2.5 lower state, which is assigned as the ground state. For the PtH band at 4367 Å, the upper state was found to be an Ω′ = 1.5 state which has been previously observed. From the dispersed fluorescence pattern from this Ω′ = 1.5 state and previous emission results we have been able to measure the spin-orbit interval between the XΩ = 1.5 and X Ω = 2.5 ground state components as 3224.9 (±0.1 ) cm −1. The corresponding Ω′ = 1.5− X2.5 (0, 0) band of PtD has also been identified at 4358 Å and has allowed us to measure a spin-orbit interval of 3228.5 (±0.1) cm −1 between the XΩ = 1.5 and XΩ = 2.5 ground state components. Although these intervals are much larger than the previously estimated value of 1200 cm −1 by Kaving and Scullman, they are in better agreement with ab initio calculations and the large atomic Pt spin-orbit ζ 5d coupling constant. Hyperfine splittings due to the I = 1 2 nuclear spin of 195Pt have been observed in both the ground state and all of the upper states. In addition, isotope splittings have been resolved for several of the upper states. Using Fourier transform spectroscopy a new band system of PtH was found in emission in the near-infrared region around 8400 cm −1. The lower state has been identified as the X1.5 ground state component and the upper state, located at 11 581.6 (±0.2) cm −1, is an Ω′ = 1.5 state of 2Π 3/2 parentage as predicted by theory. A small, low- J perturbation in the Ω′ = 1.5− XΩ″ = 1.5 (0,0) transition of PtD has allowed an independent estimate of 3227 (±3) cm −1 for the XΩ = 1.5− XΩ = 2.5 ground state spin-orbit interval, which is in excellent agreement with laser excited dispersed fluorescence data. The results of both laser excitation and Fourier transform spectroscopy confirm the assignment of X2.5 as the ground state and have enabled all the known states of PtH lobe linked in energy, including six of the ten lowest lying electronic states which are components of the Pt d 9 [ 2 D] H supermultiplet.