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>Triplet Rydberg states of the imidogen radical characterized via twohyphen;photon resonancehyphen;enhanced multiphoton ionization spectroscopy
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Triplet Rydberg states of the imidogen radical characterized via twohyphen;photon resonancehyphen;enhanced multiphoton ionization spectroscopy
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机译：Triplet Rydberg states of the imidogen radical characterized via twohyphen;photon resonancehyphen;enhanced multiphoton ionization spectroscopy
Five new triplet excited states of the ND radical (three in the case of NH) in the wavehyphen;number range 85thinsp;000ndash;91thinsp;000 cmminus;1have been identified through analysis of the twohyphen;photon resonance enhancements they provide to the wavelengthhyphen;resolved multiphoton ionization spectrum ofXthinsp;3Sgr;minus;state NH(ND) radicals. The lowest energy of these, theBthinsp;3Pgr; state, is found to be a lsquo;lsquo;regularrsquo;rsquo; Rydberg state which, on the basis of its observed quantum defect and its deduced rotational and spinndash;orbit coupling constant, is surmised to be the3Pgr; state derived from a 3psgr; electron built on the2Pgr; groundhyphen;state ion core. Perturbations are evident in theBthinsp;3Pgr;ndash;Xthinsp;3Sgr;minus;origin bands of both NH and ND. In the case of ND the perturbing state provides its own resonance enhancements, the analysis of which enables its definitive identification as theCthinsp;3Sgr;minus;state. The very small spinndash;orbit splitting found for theDthinsp;3Pgr; state is taken to indicate that (at least in the Franckndash;Condon region) its wave function is dominated by the configuration involving one 3ppgr; Rydberg electron and a4Sgr;minus;ion core. To still higher wave number we identify two more3Sgr;minus;excited states, the upper of which (theFthinsp;3Sgr;minus;state) has a very small rotational constant which we take to imply that it has substantial valence character. Further indications that theFthinsp;3Sgr;minus;(andCthinsp;3Sgr;minus;) states possess significant valence character is provided by the observation that both parent and daughter (N+) ions contribute to the overall ion yield when the multiphoton ionization proceeds via these two states. Daughterhyphen;ion formation is considered to occur via an overall fourhyphen;photon excitation process in which the coherent twohyphen;photon excitation to the3Sgr;minus;state of interest is followed by a onehyphen;photon excitation to a lsquo;lsquo;superexcitedrsquo;rsquo; state of the neutral. This is then presumed to absorb a further photon to yield the observed N+ions and/or to predissociate, yielding highly excited Nast; atoms which then undergo a direct onehyphen;photon ionization.
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