LASER SPECTROSCOPIC STUDY OF CaH IN THE B2_+ AND D2_+ STATES

Watanabe, Kyohei

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https://hdl.handle.net/2142/79247 Copy

Description

Title

LASER SPECTROSCOPIC STUDY OF CaH IN THE B2_+ AND D2_+ STATES

Author(s)

Watanabe, Kyohei

Contributor(s)

• Moriwaki, Yoshiki
• Matsushima, Fusakazu
• Kobayashi, Kaori
• Uchida, Kanako

Issue Date

22-Jun-15

Keyword(s)

Linelists

Abstract

Calcium hydride is one of the abundant molecules in the stellar environment, and is considered as a probe of stellar analysis$footnote{B. Barbuy, R. P. Schiavon, J. Gregorio-Hetem, P. D. Singh , C. Batalha , textit{Astron. Astrophys. Sippl. Ser.} textbf{101}, 409 (1993).}$. Ab initio calculations have shown that the electronic excited states of CaH have complex potential curves. It is suggested that the B$^2Sigma^+$ state has an interesting double minimum potential due to the avoided crossing$footnote{P. F. Weck and P. C .Stabcil, textit{J. Chem. Phys.} {textbf{118}}, 9997 (2003).}$. Such a potential leads to drastic change of the rotational constants when the vibrational energy level goes across the potential barrier. Spectroscopic studies on CaH began in the 1920's$footnote{R. S. Mulliken, textit{Phys. Rev.} {textbf{25}}, 509 (1925).}$, and many studies have been carried out since then. Bell et al. extensively assigned the D$^2Sigma^+-$X$^2Sigma^+$ bands in the UV region$footnote{G. D. Bell, M, Herman, J. W. C. Johns, and E. R. Peck, textit{Physica Scripta} {textbf{20}}, 609 (1979).}$. Bernath's group has observed transitions in the IR and visible regions and identified their upper states as the A$^2Sigma^+$, B$^2Sigma^+$ and E$^2Sigma^+$ states$footnote{A. Shayesteh, K. A. Walker, I. Gordon, D. R. T. Appadoo, and P. F. Bernath, textit{J. Mol. Struct.} {textbf{695-696}}, 23 (2004).}$$footnote{R. S. Ram, K. Tereszchuk, I. E. Gordon, K. A. Walker, and P. F. Bernath, textit{J. Mol. Spec.} {textbf{266}}, 86 (2011).}$$footnote{G. Li, J. J. Harrison, R. S. Ram, C. M. Western, and P. F. Bernath textit{Quant. Spectrosc. Rad. Transfer.} {textbf{113}}, 67 (2012).}$$footnote{A. Shayesteh, R. S. Ram, and P. F. Bernath, textit{J. Mol. Spec.} {textbf{288}}, 46 (2013).}$. We have carried out a laser induced fluorescence (LIF) study in the UV region between 360 and 430 nm. We have produced CaH by using laser ablation of a calcium target in a hydrogen gas environment, then molecules have been excited by a second harmonic pulse of dye laser and the fluorescence from molecules have been detected through a monochromator. Detection of the D$^2Sigma^+$-X$^2Sigma^+$ bands already identified by Bell et al. indicates the production of CaH. In addition, many other bands have been also found and a few bands have been assigned by using the combination differences, the lower state of these bands have been confirmed to the vibrational ground state of X$^2Sigma^+$ state. We have tentatively assigned these bands as the B$^2Sigma^+ -$X$^2Sigma^+$ transition. We will discuss the assignment of these bands, together with the rotational constants comparing with those calculated from the ab initio potential.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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http://hdl.handle.net/2142/79247

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