Triplet Rydberg states in molecular nitrogen

Abstract
A pulsed electric discharge in a pulsed supersonic jet of N2 is found to produce high densities of metastable E3Σ+gN2. Subsequent laser irradiation of these metastables results in single‐photon excitation to autoionizing states. Singly charged cations are detected by time‐of‐flight mass spectrometry or alternatively, ejected electrons are detected by TOF electron energy analysis. From both the laser excitation spectra and photoelectron spectra we have identified a number of autoionizing Rydberg states, including a triplet Rydberg series (np=8−26) 3ΠuE 3Σ+g converging to the ground state ion, the first member of an s‐type triplet Rydberg series 3Σ+uE converging to the B state of the ion and the lowest member of a d‐type triplet Rydberg series 3Πu and 3Σ+uE converging to the A state of the ion. Some of these transitions involve core excitations of a 3s Rydberg state configuration, resulting in a doubly excited electronic configuration [He(2sσg)2(2sσu)(2pπu)4 (2pσg)2(3sσg)]. Other transitions confirm that the E state is a mixture of a 3s Rydberg state with an X ionic core and a 3p Rydberg state with an A ionic core.

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