Experimental and theoretical studies of the radiative properties of the N2+2 D 1Σ+u state

Abstract

The fluorescence lifetime of the v’=0 level of the N²⁺₂ D ¹ ∑⁺_u electronic state has been measured, with the high frequency deflection technique, for the first time. The result, τ=6.0±0.5 ns, is in good agreement with a recent photoion–photon of fluorescence coincidence measurement which yields a lifetime, averaged over an unspecified number of vibrational levels, of 8±3 ns. The electronic transition moment function for the N²⁺₂ D ¹ ∑⁺_u–X ¹ ∑⁺_g transition was calculated with nonorthogonal complete active space SCF wave functions. Potential energy curves for the X ¹ ∑⁺_g and D ¹ ∑⁺_u states were calculated with a multireference contracted CI treatment and these potential curves were used, together with the electronic transition moment function, to obtain vibrationally averaged transition moments and hence a theoretical radiative lifetime. The calculated lifetime, 8.0 ns, is in good agreement with the experimentally determined value indicating that the decay of D ¹ ∑⁺_u, v’=0 occurs primarily via fluorescence to the X ¹ ∑⁺_g state.