Fourier-transform VUV spectroscopy of ${}^{14,15}$N and ${}^{12,13}$C

Abstract

Accurate Fourier-transform spectroscopic absorption measurements of vacuum ultraviolet transitions in atomic nitrogen and carbon were performed at the Soleil synchrotron. For ${}^{14}$N transitions from the $2s^{2}2p^3{}^4$S${}_{3/2}$ ground state and from the $2s^{2}2p^3{}^2$P and ${}^2$D metastable states were determined in the $95-124$ nm range at an accuracy of $0.025{\mathrm{cm}}^{-1}$. Combination of these results with data from previous precision laser experiments in the vacuum ultraviolet range reveal an overall and consistent offset of -0.04 \wn\ from values reported in the NIST database. %The splitting of the $2s^{2}2p^3{}^4$S${}_{3/2}$ -- %$2s2p^4{}^4$P${}_{5/2,3/2,1/2}$ The splittings of the $2s^{2}2p^3{}^4$S${}_{3/2}$ -- $2s2p^4{}^4$P${}_J$ transitions are well-resolved for ${}^{14}$N and ${}^{15}$N and isotope shifts determined. While excitation of a $2p$ valence electron yields very small isotope shifts, excitation of a $2s$ core electron results in large isotope shifts, in agreement with theoretical predictions. For carbon six transitions from the ground $2s^{2}2p^2{}^3$P${}_J$ and $2s^{2}2p3s{}^3$P${}_J$ excited states at $165$ nm are measured for both ${}^{12}$C and ${}^{13}$C isotopes.