Study of the 5p3/2 -> 6p3/2 electric dipole forbidden transition in atomic rubidium using optical-optical double resonance spectroscopy

TL;DR

This study provides direct experimental evidence of a forbidden electric dipole transition in atomic rubidium using optical-optical double resonance spectroscopy, revealing detailed hyperfine structures and confirming theoretical predictions.

Contribution

First direct observation of the 5p3/2 to 6p3/2 forbidden transition in rubidium using a Doppler-free spectroscopy method, with results matching detailed theoretical calculations.

Findings

Detected three narrow hyperfine lines (~13 MHz FWHM)

Observed F-1, F, and F+1 hyperfine splitting in spectra

Confirmed the transition's sensitivity to atomic state preparation dynamics

Abstract

Direct evidence of excitation of the 5p3/2 -> 6p3/2 electric dipole forbidden transition in atomic rubidium is presented. The experiments were performed in a room temperature rubidium cell with continuous wave extended cavity diode lasers. Optical-optical double resonance spectroscopy with counterpropagating beams allows the detection of the non-dipole transition free of Doppler broadening. The 5p3/2 state is prepared by excitation with a laser locked to the maximum F cyclic transition of the D2 line, and the forbidden transition is produced by excitation with a 911 nm laser. Production of the forbidden transition is monitored by detection of the 420 nm fluorescence that results from decay of the 6p3/2 state. Spectra with three narrow lines (~ 13 MHz FWHM) with the characteristic F - 1, F and F + 1 splitting of the 6p3/2 hyperfine structure in both rubidium isotopes were obtained. The results are in very good agreement with a direct calculation that takes into account the 5s -> 5p3/2 preparation dynamics, the 5p3/2 -> 6p3/2 non-dipole excitation geometry and the 6p3/2 -> 5s1/2 decay. The comparison also shows that the electric dipole forbidden transition is a very sensitive probe of the preparation dynamics.