Hyperfine quantum beats in C 2N 2

Abstract

Molecular quantum beats are observed in the isotropic fluorescence decay following laser excitation of individual rotational states of C 2N 2 via the vibronically allowed 4 1 0 Ã( 1Σ − u)←X̃( 1Σ + g) transition near 219 nm. Strong quantum beats occur with selective excitation, by both P- and R-branch transitions, of over a dozen rotational states. Observations of hyperfine quantum beats following excitation of the N′ = 12 rotational level yield estimates of spin—orbit coupling matrix elements, Born-Oppenheimer state separations, and magnetic and quadrupolar hyperfine coupling constants. Observations of Zeeman splitting establish that the three hyperfine levels of N′ = 12 are coupled to those of a single triplet state.