The spin-forbidden vacuum-ultraviolet absorption spectrum of 14N15N

Photoabsorption spectra of ${}^{14}\mathrm{N}{}^{15}\mathrm{N}$ were recorded at high resolution with a vacuum-ultraviolet Fourier-Transform spectrometer fed by synchrotron radiation in the range 81 to 100 nm. The combination of high column density ($3\times {10}^{17}$ cm${}^{-2}$) and low temperature (98 K) allowed for the recording of weak spin-forbidden absorption bands exciting levels of triplet character. The triplet states borrow intensity from ${}^1{\mathrm{\Pi }}_u$ states of Rydberg and valence character while causing their predissociation. New predissociation linewidths and molecular constants are obtained for the states $C{}^3{\mathrm{\Pi }}_u(v=7,8,14,15,16,21)$, $G{}^3{\mathrm{\Pi }}_u(v=0,1,4)$, and $F{}^3{\mathrm{\Pi }}_u(v=0)$. The positions and widths of these levels are shown to be well-predicted by a coupled-Schroedinger equation model with empirical parameters based on experimental data on ${}^{14}{\mathrm{N}}_2$ and ${}^{15}{\rm N}_2$ triplet levels.