Are linear molecules really linear? II. Re-interpretation of experimental B0-values

Hirano, Tsuneo

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https://hdl.handle.net/2142/100724 Copy

Description

Title

Are linear molecules really linear? II. Re-interpretation of experimental B0-values

Author(s)

Hirano, Tsuneo

Contributor(s)

• Jensen, Per
• Nagashima, Umpei

Issue Date

2018-06-19

Keyword(s)

Mini-symposium: New Ways of Understanding Molecular Spectra

Abstract

As discussed in the preceding talk, any linear triatomic molecule will be observed as being “bent” on ro-vibronic average in any ro-vibronic state.a,b,c Experimentally derived B0 constants are the results of the “observation” of Nature. This suggests that the observed B0 values are in fact those for the ro-vibrationally averaged bent structures. The easiest way to check this proposition is to interpret the set of B0 values of isotopologues taking the bond-angle as a “variable,” discarding the preconceived, conventional notion that the ro-vibrationally averaged bond angle of a linear molecule is 180◦. We have shown in previous publicationsa that bond length values derived from a set of experimental B0 values under the assumption of a linear r0 structure, is not the ro-vibrationally averaged bond lengths, but their projections onto the molecular axis. Therefore, when the projection angle is not accounted for, the bond length values obtained from the B0 values may differ significantly from the averaged bond lengths. We will show how we can derive physically sound ro-vibrational structures from the experimentally reported B0 values, taking the FeCO, NCS, HCO+, HCN, and C3 molecules as examples. The averaged bond-angle deviations from the linearity, derived from experimentally reported B0 values of multiple isotopologues, are 7.8◦, 9.5◦, 12.5◦, 14.3◦, and 23.4◦, respectively, for NCS, FeCO, HCO+, HCN, and C3 in their respective vibrational ground states. Thus, we can conclude that both theoretically (as described in the preceding talk) and experimentally (as shown here), the ro-vibrationally averaged structure of a linear molecule is observed as being bent.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100724

DOI

10.15278/isms.2018.TB03

Copyright and License Information

Copyright 2018 Tsuneo Hirano

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