THE NON-PENETRATING RYDBERG STATES OF CAF
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Date
1994
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Publisher
Ohio State University
Abstract
Nearly every member of all six core-penetrating Rydberg series ($l<3$) of CaF has been observed (from the ground state through $n^{*}=10$) and is fairly well $characterized^{1}$. The non-penetrating states ($l<2$), however, had stubbornly evaded detection. These non-penetrating states are easy to identify because they have near integer $n^{*}$ and some have anomalous rotational constants (the upper component of the complex can have an effective rotational constant about 20% larger than that of the ion) at relatively low $n^{*}$ due to rapid l-uncoupling. Non-penetrating states, which are seldom observed in molecular Rydberg spectra, provide important information about the multipole moments and polarizabilities of the $CaF^{+}$ ion that is difficult to derive from the core-penetrating series but essential for an understanding of the exchange of energy and angular momentum between the Rydberg e- and the molecular ion core. For example, it has been shown that the splittings between the different $\delta$-components of an f complex are a measure of the quadrupole $moment^{2,3}$. Most CaF Rydberg spectra were recorded in OODR fluorescence based experiments using selected rotation-vibration levels of the $A^{2}\Pi$ state as the intermediate $state^{1,4}$. Those experiments discriminate doubly (both excitation and detection) against the observation of high-$l$ states. New spectra of the Rydberg states of CaF have been recorded. These include REMPI-TOF and fluorescence-base experiments. The new fluorescence based experiments use the $C^{2}\Pi$ state as the intermediate state. The $C^{2}\Pi$ state is a member of a different Rydberg series than the $A^{2}\Pi$ state, so it has both different dominant ``l” character as well as more amplitude outside the core. Thus the $C^{2}\Pi$ state will have better overlap with the non-penetrating series. Using the $C2^{P}i$ state as the intermediate state, we have observed and assigned states with anomalously large and small effective rotational constants. The REMPI-TOF experiments complement and extend the fluorescence data into the autoinizing $v = 1, n^{*} > 12.7$ region.
Description
$^{1}$J.M. Berg, J.E. Murphy, N.A. Harris, and R.W. Field, Phys. Rev. A 48, 3012 (1993). $^{2}$Ch. Jungen and E. Miescher, Canad. J. Phys. 47, 1770 (1969). $^{3}$E.E. Eyler and F.M. Pipkin, Phys. Rev. A. 27, 2462 (1983). $^{4}$J.E. Murphy, Ph.D. Thesis, MIT (1992).
Author Institution: Department of Chemistry, M.I.T.
Author Institution: Department of Chemistry, M.I.T.