VUV electronic absorption and magnetic circular dichroism study of HI molecules

Abstract

We present the results of the first VUV (250–146 nm) magnetic circular dichroism (MCD) study of HI molecule in the gaseous state at various pressures below 1 Torr. MCD spectroscopy1 measures the difference in the absorption of right and left circularly polarized light, and refers to the situation in which a static magnetic field is applied parallel to the direction of the polarized beam. This molecule is of particular interest since it is a simple diatomic that exhibits resolved rotational, vibrational and electronic structure below the CaF2 cutoff of 140 nm. Progress in MCD measurements beyond this limit requires optics not presently available. We are investigating pressure effects and the dependence of spectra on magnetic field strength (1–5 T). The analysis of the absorption spectrum of HI molecule is also important to the proposed models of electron-nuclear momentum coupling. We are also investigating the possible role of spin-orbit mechanisms in the VUV electronic absorption and MCD of HI molecules.