The spectrum of the c-x system of N2+

The C 2 Σ + u -X 2 Σ + g system of the 14 N + 2 molecule has been investigated in the region 2300 to 1300 Å. When a discharge is passed through a mixture of helium and nitrogen, bands having v' ⩾ 3 are the only bands observed. If neon is used as a foreign gas, bands having v' ⩽ 2 also appear quite strongly. Because of the perturbation in the v' = 0, 1 and 2 levels of the C state, the vibrational constants of this state have been calculated by using the bands with v' ⩾ 3 only. Details of the excitation mechanism for this system in the mixture of nitrogen with helium and with neon are discussed. In addition to the bands of the C-X system, a few new bands, which belong to a hitherto unknown system, have been observed in the region 2510 to 2075 Å.