Experimental investigation of collisions of He atoms in the ground and metastable 2 3 S states

Mark E. Lagus

T. Hadeishi, Chung-Heng Liu

The radio-frequency paramagnetic-resonance method was used to observe the exchange collisions between the singly ionized Xe ground state $^{2}P_{\frac{3}{2}}$ and the neutral metastable state $^{3}P_{2}$. The ionic ground-state and metastable-state atoms are both formed and aligned by unidirectional low-energy high-flux electron-beam impact. The magnetic resonances of even and odd ionic ground-state atoms were observed by monitoring changes in the transparency of the resonance radiation absorbed by the metastable-state atoms. Phenomenological theories are presented which explain the sign of the magnetic-resonance signal of the ionic ground state relative to that of the neutral metastable state, together with independent experimental evidence to support the theories. Conclusive experimental evidence is presented supporting our original assumptions that the ionic ground-state ${\mathrm{Xe}}^{+}(^{2}P_{\frac{3}{2}})$ is aligned by low-energy electron-impact ionization and that such alignment is detectable through the results of exchange collisions with the metastable state.

Oleg N. Grigorashchenko, D. A. Myshkis, I. Ya. Fugol’

Tao Chen, Cui Zhang, Xiaolin Li +2 more

We theoretically explore the scattering properties in collisions between in the ground state and fermionic in the metastable state. Unlike the role of the electronic spin degree of freedom in collisions of two alkali-metal atoms, the orbital degrees of freedom from the p electron of the metastable atoms, which induce not only mixings between different partial waves but also couplings between channels in different fine-structure manifolds, introduce the anisotropic interactions for producing broad-enough Feshbach resonances. Our closed-coupling calculation shows that this mechanism is similar to that in highly magnetic atoms, but the resonances also suffer from a large inelastic rate at the magnitude of to lower-lying fine-structure states or Zeeman sublevels, which will be an obstacle for associating ultracold polar molecules with both electron spin and electric dipole momentum. However, such a rich mixture of inelastic processes, and the experimental advantage of immunity from intraspecies inelastic collisions for metastable fermionic allow for precise investigations on the interspecies scattering properties for systems with excited-state atoms included.

G.R. Woestenenk, Hennie C. Mastwijk, Jan W. Thomsen +4 more

Stephen Evans, Neal F. Lane