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The electronic spectrum of germanium methylidyne (GeCH), the prototypical organogermanium compound

TitleThe electronic spectrum of germanium methylidyne (GeCH), the prototypical organogermanium compound
Publication TypeJournal Article
Year of Publication2000
AuthorsSmith, TC, Li, HY, Clouthier, DJ, Kingston, CT, Merer, AJ
JournalJournal of Chemical Physics
Volume112
Pagination8417-8425
Date PublishedMay
Type of ArticleArticle
ISBN Number0021-9606
KeywordsMOLECULAR-STRUCTURE, PARAMETERS, SPECTROSCOPY, SYSTEM
Abstract

The (A) over tilde (2)Sigma(+)-(X) over tilde (2)Pi(i) electronic transition of jet-cooled germanium methylidyne has been recorded in the 730-555 nm region by laser-induced fluorescence techniques. The radical was produced in a pulsed electric discharge using tetramethylgermane as the precursor. The band system consists of perpendicular and vibronically induced parallel bands with upper state frequencies of nu(2)’=638/497 cm(-1) and nu(3)’=990/952 cm(-1) for GeCH/GeCD. The (2)Sigma(+)-(2)Pi(3/2) components of the 0(0)(0) bands of GeCH and GeCD and the 2(0)(1) band of GeCH have been recorded with sufficient resolution to assign the transitions of the Ge-70, Ge-72, Ge-74, and Ge-76 isotopomers. The rotational constants of the various hydrogen and germanium isotopomers were used to derive the following molecular structures: r(0)"(Ge-C)=1.775 79(21) Angstrom, r(0)"(C-H)=1.0673(12) Angstrom, r(0)’(Ge- C)=1.673 66(8) Angstrom, and r(0)’(C-H)=1.0589(5) Angstrom. The ground state germanium-carbon bond length is typical for a Ge=C double bond, but in the excited state it corresponds to a triple bond. This is a consequence of promotion of an electron from a nonbonding sigma orbital to a pi bonding orbital to form the ...sigma(1)pi(4)((2)Sigma(+)) excited state. In this study we provide the first experimental value for the length of the germanium-carbon triple bond. (C) 2000 American Institute of Physics. [S0021-9606(00)01619-6].

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