Orientation observed by Zeeman spectra of dissociated atoms and the interference in photoexcitations

In a magnetic field, the wave number of a pump laser light polarized along the field was fixed to the isolated Cs2D 1Σu+(v=46, J=54)←X 1Σg+(v=0, J=55) line, and the excitation spectrum of the dissociated Cs(6p 2P3/2) atoms was measured by scanning the wave number of a probe laser light polarized perpendicular to the field. The population of each sublevel 6p 2P3/2,mj of the dissociated atoms was determined from the line intensities in the mj-resolved excitation spectrum. The unequal population between the 6p 2P3/2,+verticalbarmjverticalbar and 6p 2P3/2,-verticalbarmjverticalbar levels (atomic orientation) was observed and it was enhanced as the magnetic-field strength was increased. The atomic orientation is shown to be induced by the interference between the indirect predissociation, which occurs by a combination of the spin-orbit coupling of the D 1Σu+ state with the (2)3Π0u state and the L-uncoupling and Zeeman interactions between the (2)3Π0u and dissociative (2)3Σu+ states, and the dissociation following a direct excitation to the (2)3Σu+ state, which is allowed by spin-orbit coupling of the (2)3Σu+ state with the B 1Πu state. It is demonstrated that the atomic orientation is produced by the photodissociation in the presence of an external magnetic field even when all degenerated molecular M=J,...,0,...,-J sublevels are excited by a light polarized linearly along the field