Experimental Deperturbation of thebΠu1←XΣg+1Transition ofN2in the Solid State, Pure and Trapped in Ne and CF4Matrices at Low Temperature

The progression observed below 1000 Å in spectra of solid ${\mathrm{N}}_2$, pure and trapped in Ne and C${\mathrm{F}}_4$ matrices at 4.2 K, is ascribed to the valence transition $b{}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{u}}^{}{}_{}{}^{}\leftarrow X{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{+}$ of ${\mathrm{N}}_2$. As previously observed in the similar case of NO, the regularity in intensity distribution and in vibrational spacings indicates the absence of the Rydberg transition $c{}_{}{}^1{}_{}{}^{}\Pi _{\mathrm{u}}^{}{}_{}{}^{}\leftarrow X{}_{}{}^1{}_{}{}^{}\Sigma _{\mathrm{g}}^{}{}_{}{}^{+}$ responsible for strong perturbations in the free-molecule spectrum.