Matter wave interferometry for measuring a molecular transition dipole moment

Abstract

Molecular matter wave interferometry was investigated for its capability of measuring molecular transition dipole moments. A pair of laser beams, tuned to a b³ $\rm\Pi_{0^+_{\it u}}$–X ¹ $\rm\Sigma^+_{\it g}$ transition, acts as beam splitters to coherently split the matter wave, forming a matter wave interferometer of the Ramsey type. An additional laser field is introduced between the two beam splitters. This field couples near resonantly the ground state level of the beam splitter transition with an excited level of the B¹ ${\rm\Pi}_u$ state. The observed shift of the matter wave interference by the AC-Stark effect is used to determine as an example the transition dipole moment of the Q(25) line of the (4-0) band of the B-X transition of K₂. The experimental result agrees well within its uncertainty limits with transition dipole moments derived from earlier lifetime measurements and from ab initio calculations of transition dipole moment functions. Thus we could demonstrate quantitatively the applicability of matter wave interferometry for determination of transition dipole moments of molecules.