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

Accurate Fourier-transform spectroscopic absorption measurements of vacuum ultraviolet transitions in atomic nitrogen and carbon were performed at the Soleil synchrotron. For ¹⁴N, transitions from the 2s²2p³ 4S_3/2 ground state and from the 2s²2p^{3 2}P and ²D metastable states were determined in the 95-124 nm range at an accuracy of 0.025 cm^-1. The combination of these results with data from previous precision laser experiments in the vacuum ultraviolet range reveals an overall and consistent offset of -0.04 cm^-1 from values reported in the NIST database. The splittings of the 2s²2p³ 4S_3/2 - 2s²p^{4 4}P_J transitions are well-resolved for ¹⁴N and ¹⁵N and the 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 2s²2p^{2 3}P_J and 2s²2p³s ³P_J excited states at 165 nm are measured for both ¹²C and ¹³C isotopes.