Spin-orbit branching ratios for the Cl atom photofragments following the excitation of Cl2 from 310 to 470 nm

Abstract

Velocity distributions for the Cl(2P3/2) and Cl(2P1/2) photofragments produced by photolysis of Cl2 in the region between 310 and 470 nm are measured using photofragment velocity mapping. Our results indicate that at short wavelengths the absorption spectrum is dominated by the 1u(1Πu) excited electronic state which produces two ground state chlorine atoms. The 0u+(B 3Πu) state which produces a spin-orbit excited and a ground state chlorine atom becomes significant at 350 nm and dominates the spectrum beyond 400 nm. Analysis of the photofragment angular distributions indicates that the Cl(2P3/2) photofragments are aligned and the magnitude of the alignment is quantitatively determined. Nonadiabatic curve crossing between the 1u(1Πu) and the 0u+(B 3Πu) electronic states is observed and quantified below 370 nm. The measured nonadiabatic transition probability is modeled using the Landau–Zener formula and the position of the curve crossing is estimated at ∼3 eV above the zero-point of ground electronic state of Cl2.