Rotationally resolved infrared absorption spectrum of N+4

The rotationally resolved infrared band of the antisymmetric stretching vibration (ν3) of N+4 has been recorded by tunable diode laser spectroscopy. A continuous supersonic expansion of pure nitrogen through a slit nozzle and electron impact ionization was employed. Forty-four P and R branch transitions with J up to 25 are observed. The band origin is at ν0=2234.5084(4) cm−1 and the rotational constants are determined to be B0=0.112 05(3) cm−1 and B1=0.111 76(3) cm−1. The infrared spectrum shows that N+4 has a linear ground state structure.