The ground-state rotational spectrum and molecular geometry of ethynylstannane.

The ground-state rotational spectra of 24 isotopomers of ethynylstannane have been observed by pulsed-jet, Fourier-transform microwave spectroscopy. The spectroscopic constants, B(0,)D(J) and D(JK) are reported for symmetric-top isotopomers H(3)(n)Sn(12)C(12)CH, where n = 116, 117, 118, 119, 120, 122 and 124, D(3)(n)Sn(12)C(12)CH, where n = 116, 118, 120, 122 and 124, H(3)(n)Sn(13)C(12) CH and H(3)(n)Sn(12)C(13)CH , where n = 116,118 and 120, and H(3)(n)Sn(12)C(12)CD, where n = 116, 118 and 120. In addition, the values of A(0), B(0), C(0), Delta(J) and Delta(JK) were obtained for the three asymmetric-top isotopomers DH(2)(n)Sn(12)C(12)CH, where n = 116, 118 and 120. Hyperfine structure was resolved and assigned in the transitions of the isotopomers H(3)(n)SnCCD, where n = 116, 118 and 120, and in the isotopomers H(3)(117)SnCCH and H(3)(119)SnCCH. In the former group, the hyperfine structure arises from D nuclear quadrupole coupling while in the latter group its origin lies in the spin-rotation coupling of the I = 1/2 Sn nuclear spin to the rotational motion. For these isotopomers, D nuclear quadrupole and spin-rotation coupling constants are determined where appropriate. The rotational constants obtained for the 24 isotopomers of H(3)SnCCH were used to obtain the following types of molecular geometry for ethynylstannane: r(0), r(s), and r(m).