Ro-vibrationally Averaged Molecular Structure Of Benzene     I. Almost The Same Bond Lengths For The C-h And C-d Bonds.

Baba, Masaaki

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https://hdl.handle.net/2142/111124 Copy

Description

Title

Ro-vibrationally Averaged Molecular Structure Of Benzene     I. Almost The Same Bond Lengths For The C-h And C-d Bonds.

Author(s)

Baba, Masaaki

Contributor(s)

• Hirano, Tsuneo
• Nagashima, Umpei

Issue Date

2021-06-25

Keyword(s)

Structure determination

Abstract

Contrary to the common sense that the C--H bond-length is longer than that of the C--D bond due to the anharmonicity of the potential, Baba group found, from high-resolution laser spectroscopy, that ro-vibrationally averaged bond lengths of C--H and C--D are observed as being almost identical ($r_{\rm 0,eff}$(C--H) $\cong$ $r_{\rm 0,eff}$(C--D)) for planar aromatic hydrocarbons, such as benzene\footnote{S. Kunishige, M. Baba, et al., J. Chem. Phys. {\bf 143}, 244302 (2015).}, naphthalene\footnote{M. Baba, U. Nagashima, et al., J. Chem. Phys. {\bf 135}, 054305 (2011).}, and anthracene\footnote{M. Baba, U. Nagashima, et al., J. Chem. Phys. {\bf 130}, 134315 (2009).}. The vibrationally averaged bond lengths of benzene deduced from experimental rotational constants and \textit{ab initio} geometry$^b$ are $r_0$(C--H) $=$ $r_0$(C--D) = 1.0831 {\AA}.$^a$ In this study, the vibrationally averaged structures of benzene are derived from the DVR (Discrete Variable Representation) wavefunction based on the 3D potential energy surface at the level of valence-CCSD(T)/[aVQZ(H,C)] theory. The zero-point C--H(D) bond-length, $r_{\rm 0,eff}$(C--H(D)), determined from the experimental effective rotational constants, is, in definition, the $r_{0}$ bond-length projected onto the $a$-$b$ principal axis plane, $r_{\rm 0,proj}$(C--H(D)). The DVR wavefunction gives $r_{\rm 0,proj}$(C--H) $=$ 1.0815 {\AA} and $r_{\rm 0,proj}$(C--D) $=$ 1.0819 {\AA}, so that the difference is of a negligibly small value $-$0.0004 {\AA}. Thus, the seemingly strange experimental finding ($r_{\rm 0,eff}$(C--H) $\cong$ $r_{\rm 0,eff}$(C--D)), which is controversial to the common sense, is resolved. The details will be given in the next presentation (part II.)

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Permalink

http://hdl.handle.net/2142/111124

DOI

10.15278/isms.2021.FK12

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