THE BOND-LENGTH OF NI2+

The rotationally resolved photodissociation spectrum of mass-selected Ni2+ has been observed. Much of the spectrum is congested and perturbe d, making the assignment of spectroscopic constants difficult. However , the use of an accidental perturbation in the upper state is shown to simplify the interpretation of the rotational structure greatly. The bond length of the vibrationless ground state of the Ni2+ ion as deter mined from the rotational constant of that state is 2.225 +/- 0.005 an gstrom. Rotational band contour analysis indicates the ground state ha s an angular momentum (spin plus orbit) along the bond axis, OMEGA'', of 9/2 which is inconsistent with the ab initio theoretical prediction of a ground 4SIGMA(g)+ state but is consistent with a 4GAMMA(g) state .