FOURIER TRANSFORM UV EMISSION SPECTROSCOPY OF THE $B{^{2}}\Sigma^{+} - X^{2}\Sigma^{+}$ BAND OF THE $PN^{+}$
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Date
1998
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Publisher
Ohio State University
Abstract
High resolution Fourier transform emission spectrum of the $B^{2}\Sigma^{+} - X^{2}\Sigma^{+}$ band of the $PN^{+}$ ion was observed in the ultra violet region around $31000 cm^{-1}$ with Bruker IFS120HR. The rotationally resolved spectrum of $PN^{+}$, produced by an ac discharge of the $PCl_{3}, N_{2}$, and He gas mixture, was recorded for about 11 h accumulating the interferogram 1600 times. The monochromator placed just before a photomultiplier worked effectively as an optical filter with a band width of $200 cm^{-1}$. The (0,0) band lines split into doublet due to the spin-rotation splitting were assigned to the R- and P- branch lines of N'' up to 35. The determined band origin $\nu_{0}=31058.9963(81) cm^{-1}$ is consistent with the previous low resolution result [1]. The rotational, centrifugal distortion constants for both states were determined as well as the spin-rotation constant for the ground state. The $B^{2}\Sigma^{+}$ state has weaker bond than that of the ground state, since the bond length of the $B^{2}\Sigma^{+} (v=0)$ state (1.570 {\AA}) is by 0.076 {\AA} longer, and the force constant ($k = 2.90$ mdyne/{\AA}) is by about 70\% smaller than those of the ground state. Present results support the ab initio calculation which predicts a shallow minimum for the $B^{2}\Sigma^{-}$ state due to avoided crossing [2]. 1. I.K. Ahmad and P.A. Hamilton, J. Mol. Spectrosc., 163, 214 (1994). 2. F. Grein, Chem. Phys. Lett., 120, 383 (1998).
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Author Institution: Department of Chemistry, Faculty of Science, Kyushu University