ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The rotational spectrum of LiBH4 was observed in the millimeter-wave region using a high- temperature absorption cell. The observed spectrum of LiBH4 showed the pattern of a symmetric top molecule: strong and weak for K=3n and 3n±1, respectively, because of the nuclear spin statistical weight for C3v symmetry. The rotational constants and centrifugal distortion constants for 7Li11BH4, 7Li10BH4, 6Li11BH4, and 6Li10BH4 species were determined. Four observed rotational constants gave rs (Li–B) to be 1.939 38±0.000 10 A(ring), which, combined with the assumption that θ(Hb–B–Ht)=113 °, led to r(B–Hb) and r(B–Ht) to be 1.256±0.015 A(ring) and 1.216(minus-plus)0.015 A(ring), respectively, where the signs should be taken in the stated order. The uncertainties of r(B–Hb) and r(B–Ht) are mainly due to that of θ (Hb–B–Ht), which is estimated to be (minus-plus)1.5 °. This bond length obtained for Li–B is much shorter than the reported value in crystal; 2.47 A(ring). The bond lengths derived indicate that LiBH4 has a tridentate molecular structure with three bridging hydrogen atoms as in the case of NaBH4, in agreement with predictions by ab initio calculations. Two sets of vibrational satellites were observed and analyzed for both 7Li11BH4 and 7Li10BH4. These satellites were assigned to the nondegenerate Li–B stretching and the doubly-degenerate Li–B–H bending mode.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.462050
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