Ba(6s6pP1,mj1)→Ba(6s6pP2,mj′3) Zeeman cross sections in single collisions withN2,O2, andH2

Zeeman cross sections [sigma][sub [ital j],][ital m[ital j]][r arrow][ital j][prime],[ital m][sub [ital j]][sup [prime]] for the spin-changing 6[ital s]6[ital p] [sup 1][ital P][sub 1]--6[ital s]6[ital p] [sup 3][ital P][sub 2] transition of barium induced by single collisions with N[sub 2], O[sub 2], and H[sub 2] have been measured using a crossed-beam apparatus. State-selective preparation of 6[ital s]6[ital p] [sup 1][ital P][sub 1,][ital m[ital j]] and detection of 6[ital s]6[ital p] [sup 3][ital P][sub 2,][ital m[ital j]][sup [prime]] was achieved using the laser excitation technique in the presence of a magnetic field that breaks the degeneracy of the magnetic sublevels. The results showed that the Zeeman cross sections [sigma]([sup 1][ital P][sub 1,][ital m[ital j]][r arrow][sup 3][ital P][sub 2,][ital m[ital j]][sup [prime]]) are fairly dependent upon [ital m][sub [ital j]] and [ital m][sub [ital j]][sup [prime]] for N[sub 2] and H[sub 2], whereas the Zeeman cross sections all have the same value with O[sub 2]. Additionally the flux-velocity contour map of Ba(6[ital s]6[ital p] [sup 3][ital P][sub 2]) for scattering with H[sub 2] depends significantly upon the magnetic sublevel of barium in the exit channel. The results for Ba-(N[sub 2],H[sub 2]) scattering were accounted for semiquantitatively by a very simple model. Themore » model was then used to stress which physical phenomena are at the origin of the preservation of the orbital alignment and orientation during collisions. The present work also compared the kind of information obtained by the direct measurement of Zeeman cross sections to that found in other experiments that deal with the effect of polarizing the collision partners.« less