Doppler-free ultraviolet excitation spectra of C ^1II_u–X^1Σ^ + _g in Na_2 by modulated population spectroscopy

Abstract

The C1Πu state of Na2 has been studied in detail by cw UV Doppler-free excitation spectra from its ground state, simplified by modulated population spectroscopy. 270 levels of e parity and 180 levels of f parity with 11 ≤ υ ≤ 35 and 8 ≤ J ≤ 70 were measured with high resolution. The observations reveal that many of the e levels with 15 ≤ υ ≤ 24 are perturbed. A likely candidate for the perturbing state is the (3)Σ1u+ state. A set of Dunham coefficients was deduced to fit the spectroscopic data after deperturbation and used to construct the Rydberg–Klein–Rees potential for the C1Πu state. In addition, Λ-type doubling of the state was observed directly.