Laser induced fluorescence (LIF) detection has been applied to measure the rotational distribution of the N2+ ion produced by double resonant multiphoton ionization of the N2 molecule. By analysis of the LIF spectra of the generated N2+ ion, the rotational propensity rules of the photoionization of N2 have been determined, which agree with theoretical prediction. The observed rotational intensity distribution shows relatively good agreement with the calculated result. Rotational relaxation of the N2+ ions by N2 collision has also been measured. The rotational relaxation rate constant is almost equal to that of the vibrational relaxation and the selection rule "symmetric" (+)↔"symmetric" (+) has been found to be obeyed.
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