A gas phase investigation of titanium monoxide and atomic titanium using high temperature photoelectron spectroscopy

Abstract

The HeI photoelectron spectra of TiO(X 3Δ) and atomic titanium have been recorded. The TiO spectrum has been assigned on the basis of ab initio ΔSCF CI calculations and by comparison with the photoelectron spectrum of atomic titanium. The first two bands of TiO were assigned to the TiO+(X 2Δ)←TiO(X 3Δ) and TiO+(A 2Σ+)←TiO(X 3Δ). No vibrational structure was resolved in the first band which was relatively weak. However, the measured band onset, (6·56±0·03) eV, leads to an estimate of an upper limit for D 0 0 in TiO+ X 2Δ of (7·13±0·10) eV. The second band was more intense and showed resolved vibrational structure. From the vibrational separations and band envelope, estimates of -w e and r e in the A 2Σ+ ionic state were obtained as (860±60) cm-1 and (1·73±0·01) Å respectively. The atomic titanium spectrum shows evidence of bands arising from both 3d and 4s ionizations and, from the measured band intensities, the 3d : 4s photoionization cross-section ratio is determined as (30·0±5·9) at the HeI photon energy.