Zeeman collision-induced

A significant drawback of trapping via a LFS Zeeman sublevel is that this opens an exothermic inelastic collision channel. During a collision, a stretched-state [76] LFS molecule can undergo a Zeeman transition to a less-trapped or even HFS state. This process is referred to as either spin relaxation [77] (as in Figure 13.5) or collision-induced Zeeman relaxation. To utilize buffer-gas loading to trap a species, this process must be sufficiently unlikely that the external motion of the molecule can be thermalized and the experiment carried out before the Zeeman state changes. 

State, which exhibits significant anisotropy in the lab frame. It is the manipulation of the rotational wavefunction by the helium interaction that governs collision-induced Zeeman relaxation of molecules. 

DOPPLER NARROWING AND COLLISION-INDUCED ZEEMAN COHERENCE IN FOUR-WAVE LIGHT MIXING... 

During the past year we have replaced the Coherent Model 599-03 by the Coherent Model 599-21. With both dye lasers actively stabilized in frequency, the instrumental resolution could be increased to 1 or 2 MHz. Although the system has not yet operated according to specifications, we have obtained new quantitative data on the linewidth of the central components. It is the purpose of this paper to present these new data. They demonstrate the phenomena of colli-sional narrowing of residual Doppler broadening in four-wave light mixing, as discussed in section 2, and of collision-induced Zeeman coherences, treated in section 3. 

Fig, 6. Narrow resonances of collision-induced Zeeman and hyperfine structure coherences (FWHM is less than. Power... 

Fig. 7. Zeeman splitting, in an external magnetic field of 10 gauss, of the four-wave mixing resonance in the geometry of Fig. 1, caused by collision-induced Zeeman coherences with Am = 1.

The mechanism of Zeeman relaxation in collisions of molecules in electronic states with nonzero electronic orbital angular momenta is different from that in collisions of E-state molecules. The response of non-E-state molecules to a magnetic field is determined by both the electron spin and the orbital angular momentum of the electrons in the open electronic shell. The orbital motion of the electrons induces electronic anisotropy, which gives rise to multiple adiabatic interaction potentials between the collision partners [20]. Consider, for example, the collision system of a hydrogen atom in an excited P state and a structureless atom, such as He. The interaction between the atoms can be described by an effective potential as a function of the interatomic distance and an angle between the direction of the electronic F-orbital and the interatomic separation line. The angular dependence of this potential is the electronic anisotropy. An alternative description of the interatomic interaction can be... 

Both Zeeman and Stark relaxation in collisions of molecules are determined by the anisotropy of intermolecular interactions. The mechanisms of Zeeman and Stark transitions in collisions of E-state molecules are, however, different. For example, Zeeman relaxation in collisions of CaH molecules with He atoms is induced by an interplay of the atom-molecule interaction anisotropy coupling different rotational states of the molecules and the spin-rotation interaction coupling the rotational... 

This spin-spin driven helium induced Zeeman relaxation is likely to be the dominant relaxation mechanism for molecules for which the spin-spin coefficient (kss) is larger than the spin-rotation coefficient (ysr). It is not clear from this qualitative model whether the additional 1 (jlb of magnetic moment gained in moving from E molecules to E states is worth the trouble. If the spin-spin driven Zeeman relaxation of E molecules is too strong, the trap lifetime will be substantially limited by inelastic collisions and not the trap depth. In 2003, a quantitative calculation was performed by Krems and colleagues that predicted a favorable Zeeman relaxation rate coefficient for imidogen (NH) with helium [35,36]. Furthermore, experiments... 

Most atoms then undergo collisions before they return to the ground state and the effect of these collisions is to induce transitions between the Zeeman levels of the excited state. 

---