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Rotational-State and Velocity-Subgroup Dependence of the Rotational Alignment of N2+ Drifted in He



E B. Anthony, V M. Bierbaum, S R. Leone


Experimental results are presented for the rotational alignment of- N2+(Ņ=O) as a function of both rotational state and component Dopplervelocity. A single-frequency ring dye laser is used to probe the alignment of N2+ drifted in helium in a flow-drift apparatus by the technique of polarized laser-induced fluorescence. The collision-induced quadrupole rotational alignment parameter Ao(2) is determined as a function of the field direction component of sub-Doppler laboratory velocity at a fixed field strength of 12 Td for five rotational states. A dramatic difference in velocity-selected alignment as a function of rotational state is observed, with the higher rotational states exhibiting a greater degree of alignment than the lower rotational states. Additionally, for sufficiently low rotational state (J = 11.5), AO^u(2) changes sign across the Doppler profile, a behavior that has not previously been reported in the literature. A companion theoretical paper presents molecular dynamics calculations that are in excellent agreement with these experimental observations.
Journal of Chemical Physics
No. 15


alignment mobility, ion, rotation


Anthony, E. , Bierbaum, V. and Leone, S. (2001), Rotational-State and Velocity-Subgroup Dependence of the Rotational Alignment of N<sub>2</sub><sup>+</sup> Drifted in He, Journal of Chemical Physics (Accessed April 14, 2024)
Created March 31, 2001, Updated October 12, 2021