Rotationally resolved fluorescence excitation spectrum produced through photoexcitation of the coupled and b′(1) states of N2

Employing a high-resolution spectrometer in a synchrotron radiation facility we have demonstrated the feasibility of studying rotationally resolved fluorescence excitation spectra (FES) in the extreme ultraviolet region. Specifically, we have obtained FES spectrum of the (1,0) band of the b′ 1Σu+–X 1Σg+ transition using a resolution of 0.0024 nm and the resonance FES of the (0,0) band of the c ′ 4 1Σu+–X 1Σg+ transition using a resolution of 0.0048 nm produced through photoexcitation of N2 in the spectral region between 95.75 and 96.00 nm. Strong local rotational perturbation between the c ′ 4 ( 0 ) and the b′(1) states occurring at excited rotational levels J′ = 10 and 11 has been confirmed in the FES of the b′ 1Σu+–X 1Σg+ transition, in excellent agreement with early absorption spectroscopic study. From the observed relative fluorescence intensities we conclude that the production of the intense emission of the (1,0) b′–X transition is at the expense of the (0,0) c ′ 4 – X emission of N2. The c ′ 4 ( 0 ) state apparently prefers to radiate back to the ground electronic state while the b′(1) state appears to favor branching to the a 1Πg state and the subsequent a 1Πg → X 1Σg+ transition.