observation of 5P-6P optical forbidden transition in laser-cooled rubidium atoms

Alina Gearba, Brad Crochet, Kileigh Peturis +1 more

A. Pietiläinen, A. Äijälä, H. Ludvigsen +2 more

F. Ponciano-Ojeda, Santiago Hernández-Gómez, Cristian Mojica-Casique +8 more

An advanced undergraduate experiment to study the 5P3/2→6P3/2 electric quadrupole transition in rubidium atoms is presented. The experiment uses two external cavity diode lasers, one operating at the D2 rubidium resonance line and the other built with commercial parts to emit at 911 nm. The lasers produce the 5s→5p→6p excitation sequence in which the second step is the forbidden transition. Production of atoms in the 6P3/2 state is observed by detection of the 420 nm fluorescence that results from electric dipole decay into the ground state. Lines whose widths are significantly narrower than the Doppler width are used to study the hyperfine structure of the 6P3/2 state in rubidium. The spectra illustrate characteristics unique to electric dipole forbidden transitions, like the electric quadrupole selection rules; they are also used to show general aspects of two-color laser spectroscopy such as velocity selection and hyperfine pumping.

拓馬 伊藤

T. A. Vartanyan, A. E. Logunov, Anatoly S. Pazgalev +3 more

The changes in the states of excited Rb atoms approaching a single-crystal sapphire surface have been investigated by methods of laser-excitation spectroscopy and luminescence of Rb vapor in a cell with sapphire windows, the gap between which was varied from 250 to 500 nm. Upon resonant excitation of Rb atoms by two semiconductor lasers with powers of 20 and 40 mW, luminescence from optically excited 5D 3/2 and 5D 5/2 states and optically unexcited 6P 1/2 and 6P 3/2 states is observed. It is established that the luminescence intensity from unexcited states is only a few times lower than that from excited states, with allowance for the fact that excited atoms are rapidly and almost completely quenched on the sapphire surface. The found anomalously strong luminescence from optically unexcited 6P J states is explained by their nonradiative occupation near the sapphire surface from optically excited 5P J states, in which atoms fail to reach the sapphire surface because of the repulsion from it. This repulsion is due to the polarization interaction between sapphire and the atoms in the 5P J states near the surface. Nonradiative transition from the 5P J state to the 6P J −1 state is accompanied by excitation of two optical phonons in sapphire.

Georg A. Raithel