Fourier Transform Microwave Measurements of the Quadrupole Hyperfine Structure of NaBH4and KBH4

Microwave spectrum of alkali metal tetrahydroborate. III. Rotational transitions of LiBD4, NaBD4, and KBH4 in the ground vibrational states and molecular structures of MBH4 (M=Li, Na, and K)

“…Rotational transitions of LiBD 4 , NaBD 4 , and KBH 4 in the ground vibrational states and molecular structures of MBH 4 (M‫؍‬Li, Na, and K) Yoshiyuki In order to determine the molecular structure of alkali metal tetrahydroborates in a systematic way, we have extended the measurements of rotational transitions to LiBD 4 , NaBD 4 , and KBH 4 in the ground vibrational states. The observed spectra, which all conformed well to the pattern expected for a symmetric top molecule, yielded rotational and centrifugal distortion constants for 7 Li 11 BD 4 , 7 Li 10 BD 4 , 6 Li 11 BD 4 , 6 Li 10 BD 4 , Na 11 BD 4 , Na 10 BD 4 , 39 K 11 BH 4 , 39 K 10 BH 4 , and 41 K 11 BH 4 . The four observed rotational constants of LiBD 4 gave r s ͑Li-B͒ to be 1.931 09͑14͒ Å, which, when combined with an assumption that ͑D b -B-D t ͒ϭ113.0°, led to r͑B-D b ͒ and r͑B-D t ͒ to be 1.250Ϯ0.025 Å and 1.212ϯ0.032 Å, respectively, where the uncertainties of the B-D distances are primarily due to that of ͑D b -B-D t ͒ estimated to be ϯ1.0°.…”

“…Before searching for the spectral lines, the rotational constants of 7 Li 11 BD 4 , 7 Li 10 BD 4 , 6 Li 11 BD 4 , and 6 Li 10 BD 4 were estimated using the structural parameters reported in a previous paper 1 to be 18 798, 19 010, 20 319 and 20 519…”

“…The present paper reports the rotational spectra thus obtained with their structural implications; the data on LiBD 4 and NaBD 4 will supplement those obtained for LiBH 4 and NaBH 4 in previous studies. 1,2 In a separate study, 6 we have observed the lowest rotational transition Jϭ1←0 of NaBH 4 and KBH 4 by using a Fourier trans-form microwave spectrometer in order to determine the boron nuclear quadrupole coupling constants and the dipole moments precisely.…”

High resolution laser excitation spectroscopy of the B̃E2-X̃A12 transitions of calcium and strontium monoborohydride

“…The experimental work [9][10][11][12][13][14][15][16][17][18] has consisted primarily of microwave spectroscopic investigations in the gas phase. In these studies, the rotational and hyperfine parameters have been determined for the ground electronic states of NaBH 4 , [9][10][11][12] NaBD 4 , 10,13 LiBH 4 , 10,14,15 LiBD 4 , 13 and KBH 4 . 11,13 Based on isotopic data, lithium and sodium borohydrides were found to possess the tridentate structure in the ground state.…”

“…In these studies, the rotational and hyperfine parameters have been determined for the ground electronic states of NaBH 4 , [9][10][11][12] NaBD 4 , 10,13 LiBH 4 , 10,14,15 LiBD 4 , 13 and KBH 4 . 11,13 Based on isotopic data, lithium and sodium borohydrides were found to possess the tridentate structure in the ground state. Theoretical studies [19][20][21][22][23][24][25][26][27][28] have also predicted this geometric configuration for the ground state.…”