Laser Spectroscopy of the Hydrogen Molecular ion HD⁺

Abstract

The hydrogen molecular ion is the simplest bound system that can be called a molecule. Therefore it plays a role in the theory of molecular structure that corresponds to the role of the hydrogen atom in atomic structure theory. The experimental situations, however, little resemble each other, for while the hydrogen atom spectrum is among the most precisely and the earliest studied, that of the hydrogen molecular ion has languished until recently among the “forgotten poor,” spectroscopically speaking. In this talk I will summarize briefly the work [1] several colleagues and I are doing in this area. While by comparison with some of the other spectroscopic experiments reported at this conference it is not yet correct to call our results extremely precise, we have at least been able to uplift the hydrogen molecular ion spectrum to “middle-class respectability,” and have been able to make a significant test of the first-principles theoretical calculations of its spectrum. Our absolute accuracy, as I will show, now is a few parts in 10⁷.