Vibration-rotation spectroscopy of the HD+ion near the dissociation limit

Abstract

We have re-examined the R branch of the 18–16 band in HD⁺ with a new ion beam machine which provides increased sensitivity. Using tightly focused infrared laser beams of 20 to 30 W c.w. we observe weak satellite lines which accompany the main vibration-rotation lines. These satellites arise from nuclear hyperfine interactions, and their intensities and relative frequencies have been measured and analysed. We are able to determine the deuterium Fermi contact interaction constants for v=16 and 18, which show that, in these vibrational levels, the electron distribution is essentially symmetric. Detailed intensity considerations indicate that the weakest satellite lines observed correspond to oscillator strengths of 10⁻¹¹ and future possibilities are discussed in the light of the high sensitivity achieved.