Spin Polarization of Rb and Cs np P 2 32 (n=5, 6) Atoms by Circularly Polarized Photoexcitation of a Transient Diatomic Molecule

We report the selective population of Rb or Cs np P232 (n=5, 6; F=4, 5) hyperfine states by the photodissociation of a transient, alkali-rare gas diatomic molecule. Circularly polarized (σ-), amplified spontaneous emission (ASE) on the D2 line of Rb or Cs (780.0 and 852.1 nm, respectively) is generated when Rb-Xe or Cs-Xe ground state collision pairs are photoexcited by a σ+-polarized optical field having a wavelength within the D2 blue satellite continuum, associated with the BΣ212+←XΣ212+ (free←free) transition of the diatomic molecule. The degree of spin polarization of Cs (6p P322), specifically, is found to be dependent on the interatomic distance (R) at which the excited complex is born, a result attributed to the structure of the BΣ212+ state. For Cs-Xe atomic pairs, tuning the wavelength of the optical field from 843 to 848 nm varies the degree of circular polarization of the ASE from 63% to almost unity because of the perturbation, in the 5≤R≤6 Å interval, of the Σ212+ potential by a dσ molecular orbital associated with a higher Λ2 electronic state. Monitoring only the Cs 6p P322 spin polarization reveals a previously unobserved interaction of CsXe (BΣ212+) with the lowest vibrational levels of a Λ2 state derived from Cs (5d)+Xe. By inserting a molecular intermediate into the alkali atom excitation mechanism, these experiments realize electronic spin polarization through populating no more than two np P232 hyperfine states, and demonstrate a sensitive spectroscopic probe of R-dependent state-state interactions and their impact on interatomic potentials.