REVISED SPECTROSCOPIC CONSTANTS AND VIBRATIONAL ASSIGNMENT FOR THE $B ^{*}\Pi_{0u}{^{+}}$ STATE OF IODINE$^{\ast}$
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Date
1964
Journal Title
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Publisher
Ohio State University
Abstract
The previously accepted vibrational and rotational constants for the B state of iodine are unable to reproduce accurately either the observed absorption spectrum or the intensity distribution in $fluorescence.^{1}$ We have remeasured portions of the B-X absorption system, using a 10-meter echelle-grating spectrograph at a resolving power of approx. 600,000. A new analysis of 719 line in the $6^{\prime\prime}-3^{\prime}, 7^{\prime\prime}-4^{1}, 4^{\prime\prime}-5^{1}, 5^{\prime\prime}-7^{1}, 1^{\prime\prime}-11^{1}, 2^{\prime\prime}-2^{1}, 2^{\prime\prime}-13^{1}, 0^{\prime\prime}-25^{1}$, and $0^{\prime\prime}-29^{1}$ bands, combined with previous measurements by $Mecke,^{2}$ $Loomis,^{3}$ and R. L. $Brown,^{4}$ gives the following revised constants. [FIGURE]$\omega_{e}{^{1}} = 125.077 cm^{-1} B_{e}{^{1}} = .028969 cm^{-1} \omega_{e}x_{e}{^{1}} = .6830 \alpha_{e}{^{1}} = .0001561 \omega_{e}y_{e}{^{1}} = -.00633 \gamma_{e}{^{1}}= -4.03 \times 10^{-7} \omega_{e}z_{e}{^{1}}= +.000039 \delta_{e}{^{1}} = -3.5 \times 10^{-8} D_{e}{^{1}}= 4378. D_{e}{^{1}}\cong 3.5 \times 10^{-9} T_{e}{^{1}} = 15784. \beta_{e}{^{1}}\cong 3.9 \times 10^{-10}$ Combination differences for ground state levels will also be reported and compared with Rank's most recent $determinations.^{5}$ Using these new constants, it was still found impossible to compute the correct Franck-Condon factors, using a numerical Rydberg-Klein-Rees method to obtain the potential, and a L\ddot{o}wdin iteration-variation procedure with numerical integration to solve the radial Schr\ddot{o}dinger $equation,^{6}$ so long as the vibrational numbering originally $assigned^{2,3}$ was retained. We found that decreasing the vibrational numbering of the B state by one unit brought the calculated intensity distribution and all observed fluorescence data into complete agreement.
Description
$^{\ast}$ Supported by the National Science Foundation and the Atomic Energy Commission. $^{1}$ R. N. Zare, UCRL--11110; J. Chem. Phys. 40 (1964), in press. $^{2}$ R. Mecke, Ann. d. Physik 71, 104 (1923) $^{3}$ F. W. Loomis, Phys. Rev. 29, 112 (1927). $^{4}$ R. L. Brown, Thesis, Harvard University (1963); R. L. Brown and D. Griffiths, unpublished data. $^{5}$ D. H. Rank and B. S. Rao, J. Mol. Spectroscopy 12 (1964), in press. $^{6}$ R. N. Zare, UCRL--10925.
Author Institution: Department of Chemistry, Harvard University
Author Institution: Department of Chemistry, Harvard University