Improved rotational characterization of the E3Σ1+(63S1) Rydberg state of CdAr van der Waals diatom: Excitation of single-isotopologue and <i>J</i>-level population distribution

Abstract

An improved rotational characterization of the E3Σ1+(63S1) Rydberg state of the CdAr diatom produced in a supersonic beam and studied using laser induced fluorescence (LIF) excitation spectra is presented. As an example, the spectra of the E3Σ1+←A3Π0+(53P1) transition, originating from the excitation of a single 116Cd40Ar isotopologue, are recorded and analyzed. In the experiment, the optical–optical double resonance method is employed, utilizing the E3Σ1+(υ′)←A3Π0+(53P1)(υ″=6)←X1Σ0+(υ=0) scheme. The excitation of a single isotopologue and the influence of the first-step excitation wavenumber on rotational level population distribution are carefully investigated, facilitating the simulation of the recorded rotational profiles. Spectra of several υ′ ← υ″ = 6 vibrational components are measured. Their analysis resulted in the determination of Be′, αe′, and βe′ rotational constants. In addition, the Re′ bond length in the E3Σ1 in+ Rydberg-state inner well of 116Cd40Ar was determined. For comparison, LIF excitation spectra in multi-isotopologue excitation are discussed.