Laser-rf double-resonance study of N2+

We have applied the laser-rf-laser double-resonance method to a molecular ion. Fifty-six hyperfine components of fine-structure transitions (J=1) were measured in rotational levels from N=1 to 27 of the 1/2=1 vibrational level of the X2 g+ ground electronic state of N2+14. In order to fit the data, we required seven molecular constants, corresponding to the following interactions: electron spin-rotation fine structure and its centrifugal distortion, Fermi-contact hyperfine structure (hfs), dipolar hfs and its centrifugal distortion, and electric quadrupole and nuclear spin-rotation hfs. The results are in reasonable agreement with theoretical calculations based upon a Hartree-Fock-Roothaan wave function.