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We have measured the linear and circular polarization of 391.4 nm N 2P-branch fluorescence produced by spin-polarized electron impact excitation of N 2 X 1 ⌺ g + ͑v =0͒ ground states.The resulting nonzero values of the circular polarization indicate that spin-rotation coupling, in conjunction with electron exchange excitation, acts to produce oriented rotational angular momenta in the excited molecular state prior to decay.

We have investigated helium (1s3d) 3 D → (1s2p) 3 P (588 nm) fl uorescence produced by electron impact excitation in the vicinity of the (2s 2 2p) 2 P and (2s2p 2 ) 2 D negative-ion resonances at 57.2 and 58.3 eV, respectively. In contrast to previous work, we use spin-polarized incident electrons and report the relative Stokes parameters P 1 , P 2 , and P 3 in the 55-60 eV region. Our failure to see discernable resonance effects in P 2 indicates that even though the lifetime of these resonances is signifi cant (~10 fs), magnetic forces acting on the temporarily captured electron are small. Resonant structures in the values of P 1 and P 3 are observed because the polarization contributions of resonant states are generally different than those from direct excitation of the 3 3 D state.

Using H2 and D2 targets, we have measured the polarization of Fulcher-band fluorescence resulting from spin-polarized electron-impact excitation of vibrationally and rotationally resolved d 3Π(u) → a 3Σ(g)+ transitions for incident electron energies from 14.3 to 28.5 eV. Near threshold, the linear polarization P1 descends from positive values through zero to negative values, indicating a dynamic production of M(N)=0 states. The circular polarization P3 is measured to be nonzero, indicating the orientation of rotationally resolved molecular states. For Q-branch transitions, P3 is consistent with theory based on Hund's case (b) coupling. The R-branch P3 values do not agree with theory equally well, indicating the effect of Σ-symmetry perturbation of the parent d 3Π(u)+ state.