THE SPECTRUM AND ENERGY LEVELS OF SINGLY IONIZED CESIUM
Abstract
The cesium spectrum emitted by a pulsed radio-frequency discharge has been measured in the 1550 (ANGSTROM) to 4 (mu)m spectral region using concave grating spectrographs, Fabry-Perot interferometry, and Fourier spectroscopy. The source was adjusted to optimize the excitation of singly ionized cesium, and 1732 lines believed to belong to Cs II were observed. Most of these lines (1677) have been classified as transitions between 118 even and 170 odd energy levels. Of these 288 levels, 236 were located as a result of this experimental work. All of the low-lying Cs II configurations are complete and have been interpreted by least-squares analysis to obtain empirical energy parameters and intermediate-coupling wave functions. Most excited configurations show rather good jK coupling, hence all levels have been assigned designations in the jK coupling notation. The hyperfine structure that is a prominent feature of many Cs II lines has been studied extensively by analyzing hyperfine patterns in high-resolution Fourier spectra. Hyperfine splitting constants have been determined for 167 levels. No attempt has been made to give a theoretical interpretation of the splitting factors, but we have noted regularities in the splitting constants which have been used in a phenomenological way to aid in the classification of energy levels. A number of Rydberg series of levels with as many as 7 to 11 members have been found and used to estimate the Cs II ionization limit by fitting an extended Ritz formula to the observed levels. Based on the three unperturbed series (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) and (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) the ionization limit has been found to be 186777.4(3) cm('-1). In addition to Cs II transitions, many lines belonging to Cs I and Cs III were observed. The Cs I data include nearly 100 lines with wavelengths greater than 1 (mu)m. These data represent the first comprehensive and precise measurement of the Cs I infrared region. Among the lines not previously observed were found the 4f-ng transitions which establish the ng('2)G levels for n = 6 - 11. By varying the operating conditions of the pulsed rf source, it was possible to distinguish between the lines of CS II and CS III. Approximately 600 Cs III lines were measured of which 470 have been classified as transitions between 53 even and 44 odd levels. Sixty-four of these levels are newly found. All of the new levels were assigned designations in the LS coupling representation by comparison with ab initio predictions of the Cs III level structure. Additional theoretical interpretation is needed to determine more meaningful designations.
Degree
Ph.D.
Subject Area
Atoms & subatomic particles
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