Rotational spectrum and structure of the Ne–HCN dimer

Abstract

Microwave rotational transitions have been observed at low J (0-3) for several isotopic species of the Ne-HCN dimer using the Balle/Flygare Mark II Fourier transform spectrometer with a pulsed nozzle as the source. For 2oNe-HC 14N, the main K =0 transitions give rotational constants B, D J, and H J of 2772.816 and 1.280 MHz and 1.173 kHz. The 14N nuclear quadrupole constant increases linearly with J(J+ 1) at a slope Dx of -12.7 kHz fro~ a value for Xa( 14 N) of -0.957 MHz at J=O. The pseudodiatomic approximation for Band Xact 4 N) leads to a value of 3.89 A for the Ne to HC 14N center-of-mass (c.m.) distance R, and to 46.8° for the "average" bend angle () of HC 14N. Some of the K=O, J= 1 ..... 2, and J=2 ..... 3 transitions exhibit one or two weak satellites -30 MHz away, usually below, but also both above and below. The J= 1 ..... 2 low frequency satellites for 2oNe-HC 14N and 2oNe_ HC 15N, nominally 1 11 ..... 2 12 , are symmetrical doublets with splittings of 305 and 439 kHz, respectively. The 14N hyperfine structure (hfs) is identical for the two 2oNe-HC 14N components as is the Stark effect for 2oNe-HC 15N. The molecular mechanics for clusters (MMC) model was used to calculate potential energy surfaces for Rg-HCN dimers, giving stabilities of 21, 37, 85, and 108 cm -I with He, Ne, Ar, and Kr as the rare gas. A qualitative comparison of the experimental properties for the dimers with Ne, Ar, and Kr as the rare gas is based on the surfaces. The extremely mobile internal dynamics of Ne-HCN are attributed to its potential surface, which is both very shallow and isotropic.

Six-Dimensional Energy-Switching Potential Energy Surface for HeHCN

“…A host of workers 17,18,21,24,25 experimentally investigated this van der Waals complex, although arriving at no general consensus on the form of its potential energy surface. 22 Gutowsky et al, 3 while investigating experimentally the microwave rotational transitions of Ne-HCN dimer, have also presented a molecularmechanics-for-clusters (MMC) potential energy surface for Rg-HCN dimers with He, Ne, Ar, and Kr as rare gas giving stabilities of 21, 37, 85, and 108 cm -1 , respectively. Their results also show a quasilinear equilibrium geometry for both He-HCN and Ne-HCN dimers.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Monomers and dimers were investigated both experimentally and theoretically. 3,4,9,[16][17][18][19][20][21][22][23] An ab initio CEPA-I and MP4 potential energy surface for ArHCN was reported by Clary et al 2 and Tao et al, 22 respectively. A host of workers 17,18,21,24,25 experimentally investigated this van der Waals complex, although arriving at no general consensus on the form of its potential energy surface.…”

Rotational spectrum and structure of an (H2O–HCN)–Ar trimer

“…So initially we attempted to fit sg and the Jϭ0→1 frequency ͑BϩC or AϩC͒ with exotic Ar-HCN and Ar 2 -HCN structural variations more or less compatible with the ''ordinary'' structures reported. 10,18 These efforts were unsuccessful but with the aid of MMC calculations it became apparent that we were dealing with a heterotrimer, of which a T-shaped ͑H 2 O-HCN͒-Ar was the most likely candidate. This encouraged a more systematic study of the species.…”

“…2͑a͒ for the Ar-HCN dimer is very shallow ͑85 cm Ϫ1 ͒ and broad, characteristic of a weak quasilinear structure. 1,10 There is some indication, not shown, of an even weaker ͑5 cm Ϫ1 ͒ secondary minimum at the linear HCN-Ar configuration. 10 The curve in Fig.…”

“…1,10 There is some indication, not shown, of an even weaker ͑5 cm Ϫ1 ͒ secondary minimum at the linear HCN-Ar configuration. 10 The curve in Fig. 2͑b͒ for the ͑HCN͒ 2 -Ar trimer is displaced to much lower E by the formation of the strong HCN-HCN hydrogen bond ͑1500 cm Ϫ1 ͒.…”