Abstract: The spectra of N2O+ ions in A2Σ+ state have been investigated. Pure parent N2O+ ions, in the X2Π3/2,1/2(000) state, were prepared by (3+1) multiphoton ionization of jet-cooled N2O molecules using a laser beam at 360.55 nm. By introducing another laser, the parent ions were excited to the predissociative A2Σ+ state, and the fragment NO+ was detected by a time-of-flight mass spectrometer. The NO+ photofragment excitation (PHOFEX) spectra were recorded by scanning the dissociation laser in the wavelength range of 278—328 nm. The PHOFEX spectra could be attributed completely to the A2Σ+←X2Π transition of N2O+, in which most vibronic bands were observed for the first time. By considering the Fermi resonance between the ν1 and ν2 modes, the spectra were assigned, and the spectral constants, such as vibrational frequencies, anharmonic constants, and Fermi interaction constant, were obtained with relatively high reliability and precision.

Keywords: 
• N2O+ ions A2Σ+ state /
• PHOFEX /
• Fermi resonance /
• spectral constants