Radiative transition parameters of the [formula omitted] band system

Abstract

The relative band strengths of several absorption bands of the Ag 2 C 1 Π u – X 1 Σ g + system are measured for the first time. Ratios of observed strengths for bands with common lower vibronic levels are compared with theoretically predicted absorption band oscillator strengths, which we computed by numerically solving the radial Schrödinger equation for the vibrational wave functions, ψ υ ′ and ψ υ ″ of the Ag 2 107 , 109 C 1 Π u – X 1 Σ g + band system, using Rydberg–Klein–Rees potential energy curves and a suitable choice for the electronic transition moment function. This resulted in a useful set of radiative transition parameters for a large matrix of Ag 2 C– X bands. The functional form of the electronic transition moment required by the observed band strength ratios forces good agreement between the observations and diatomic molecular theory. Since the function is highly nonlinear, the commonly applied r-centroid approximation is invalid, and numerical integration of ∫ ψ υ ′ * R e ( r ) ψ υ ″ dr had to be performed instead. As a final check on the reliability of our results, we find good agreement between the experimentally measured displacements of band heads for the Ag 2 107 , 107 and Ag 2 109 , 109 isotopologues and the corresponding isotopic shifts of our calculated band origins.