High resolution absorption spectrum of N2O between 75 000 and 104 000 cm(-1)

The absorption spectrum of N2O was photographed at a resolution limit of 0. 0008 nm, from 134 nm to the ionization potential, at 96 nm. Ab initio calcu lations of the electronic energies and transition moments were carried out including spin-orbit interaction in the frozen core approximation. Rydberg states considered are those corresponding to l=0-5 and principal effective quantum number n* up to 5.5 (6s and 6p, 5d, 5f, and 5g terms), and three io nic cores (X) over tilde (2)Pi, (A) over tilde (2)Sigma (+), and (B) over t ilde (2)Pi. It is shown that in N2O, like in CO2 or CS2, np pi terms are at lower energy than np sigma. The strongest band of the low-resolution absor ption spectrum, at about 77 900 cm-1 is too broad and diffuse to be observe d here. It is assigned to the origin of the ...2 pi (3)3p pi (1)Sigma (+)-( X) over tilde (1)Sigma (+) transition. The most prominent bands in the 84 0 00-104 000 cm(-1) interval are the electronic origins of the ...2 pi (3)np sigma transitions, observed from n=3 to n=19. Previous low-resolution absor ption and resonance enhanced multiphoton ionization spectra are reviewed in the light of the present results. (C) 2001 American Institute of Physics.