Microwave spectra and ab initio studies of Ar-propane and Ne-propane complexes: Structure and dynamics

Peterson, Karen I.; Pullman, David; Wei Lin; Minei, Andrea J.; Novick, Stewart E.
November 2007
Journal of Chemical Physics;11/14/2007, Vol. 127 Issue 18, p184306
Academic Journal
Microwave spectra in the 7–26 MHz region have been measured for the van der Waals complexes, Ar–CH3CH2CH3, Ar–13CH3CH2CH3, 20Ne–CH3CH2CH3, and 22Ne–CH3CH2CH3. Both a- and c-type transitions are observed for the Ar-propane complex. The c-type transitions are much stronger indicating that the small dipole moment of the propane (0.0848 D) is aligned perpendicular to the van der Waals bond axis. While the 42 transition lines observed for the primary argon complex are well fitted to a semirigid rotor Hamiltonian, the neon complexes exhibit splittings in the rotational transitions which we attribute to an internal rotation of the propane around its a inertial axis. Only c-type transitions are observed for both neon complexes, and these are found to occur between the tunneling states, indicating that internal motion involves an inversion of the dipole moment of the propane. The difference in energy between the two tunneling states within the ground vibrational state is 48.52 MHz for 20Ne–CH3CH2CH3 and 42.09 MHz for 22Ne–CH3CH2CH3. The Kraitchman substitution coordinates of the complexes show that the rare gas is oriented above the plane of the propane carbons, but shifted away from the methylene carbon, more so in Ne propane than in Ar propane. The distance between the rare gas atom and the center of mass of the propane, Rcm, is 3.823 Å for Ar-propane and 3.696 Å for Ne-propane. Ab initio calculations are done to map out segments of the intermolecular potential. The global minimum has the rare gas almost directly above the center of mass of the propane, and there are three local minima with the rare gas in the plane of the carbon atoms. Barriers between the minima are also calculated and support the experimental results which suggest that the tunneling path involves a rotation of the propane subunit. The path with the lowest effective barrier is through a C2v symmetric configuration in which the methyl groups are oriented toward the rare gas. Calculating the potential curve for this one-dimensional model and then calculating the energy levels for this potential roughly reproduces the spectral splittings in Ne-propane and explains the lack of splittings in Ar-propane.


Related Articles

  • Triplet dipoles in the absorption spectra of dense rare gas mixtures. I. Short range interactions. Guillot, Bertrand; Mountain, Raymond D.; Birnbaum, George // Journal of Chemical Physics;1/15/1989, Vol. 90 Issue 2, p650 

    A theory is proposed to evaluate the induced-dipole moment occuring when three dissimilar atoms are mutually interacting. Based on the one-effective electron model, the theory predicts that, at short and intermediate distances, the triatomic dipole moment originates from three different...

  • The torsional spectrum of CH3CH3. Moazzen-Ahmadi, N.; Gush, H. P.; Halpern, M.; Jagannath, H.; Leung, A.; Ozier, I. // Journal of Chemical Physics;1/15/1988, Vol. 88 Issue 2, p563 

    The perturbation-allowed torsional spectrum of gaseous CH3CH3 has been measured between 225 and 340 cm-1 at a resolution of 0.015 cm-1 using a Fourier transform spectrometer. The absorption path length was 124 m; the gas temperature and pressure were 295 K and 107 Torr, respectively. The P, Q,...

  • Far-infrared permanent and induced dipole absorption of diatomic molecules in rare-gas fluids. I. Spectral theory. Roco, J. M. M.; Hernández, A. Calvo; Velasco, S. // Journal of Chemical Physics;12/1/1995, Vol. 103 Issue 21, p9161 

    We present a spectral theory for the far-infrared absorption spectrum of a very diluted solution of diatomic molecules in a rare-gas fluid, that includes permanent and induced contributions. The absorption coefficient is given as the convolution of a translational spectrum and a rotational...

  • The isomers of HF–HCN formed in helium nanodroplets: Infrared spectroscopy and ab initio calculations. Douberly, G. E.; Miller, R. E. // Journal of Chemical Physics;1/8/2005, Vol. 122 Issue 2, p024306 

    Binary complexes containing hydrogen cyanide and hydrogen fluoride are formed in helium nanodroplets, and studied using high-resolution infrared laser spectroscopy. Rotationally resolved spectra are reported for the H–F and C–H stretches of the linear HCN–HF complex, a...

  • Binary rototranslational hyper-Rayleigh spectra of H2–He gas mixture. Godet, J.-L.; Bancewicz, T.; Głaz, W.; Maroulis, G.; Haskopoulos, A. // Journal of Chemical Physics;11/28/2009, Vol. 131 Issue 20, p204305 

    The collision-induced rototranslational hyper-Rayleigh spectra of gaseous H2–He mixture are computed and discussed in the binary regime. As the input data we use our ab initio computed H2–He collision-induced first dipole hyperpolarizability tensor Δβ(R). Both the vector and...

  • Computed lifetimes of metastable states of the NO2+ dication. Baková, R.; Fišer, J.; Šedivcová-Uhlíková, T.; Špirko, V. // Journal of Chemical Physics;4/14/2008, Vol. 128 Issue 14, p144301 

    Based on the ab initio potential energy, spin-orbit coupling,electronic transition dipole moment, and radial nonadiabatic coupling functions, the energy level positions, lifetimes, and radiative transition probabilities (Einstein A coefficients) have been determined for the lowest electronic...

  • Microwave spectrum, centrifugal perturbation, dipole moment, and conformation of 5-methyl-1,3-dioxane. Mamleev, A. Kh.; Galeev, R. V.; Gunderova, L. N.; Faizullin, M. G.; Shapkin, A. A. // Journal of Structural Chemistry;Jul2008, Vol. 49 Issue 4, p639 

    The microwave spectrum of 5-methyl-1,3-dioxane was studied in the frequency range 12–35 GHz. The a and c type rotation transitions with J≤30 were identified. The rotational constants A = 4658.5244(33) MHz, B = 2383.3930(12) MHz, and C = 1724.28907(88) MHz and the quartic constants...

  • The permanent electric dipole moments of WN and ReN and nuclear quadrupole interaction in ReN. Steimle, Timothy C.; Virgo, Wilton L. // Journal of Chemical Physics;12/22/2004, Vol. 121 Issue 24, p12411 

    The high-resolution laser induced fluorescence spectra of tungsten mononitride WN and rhenium mononitride ReN have been recorded in a laser ablation/molecular beam spectrometer. The field free spectrum of the (0,0)A 4Π3/2-X 4Σ1/2- band system of 186WN has been analyzed to produce B″,...

  • Vibrational spectra from atomic fluctuations in dynamics simulations. II. Solvent-induced frequency fluctuations at femtosecond time resolution. Schmitz, Matthias; Tavan, Paul // Journal of Chemical Physics;12/22/2004, Vol. 121 Issue 24, p12247 

    The midinfrared (MIR) spectra of molecules in polar solvents exhibit inhomogeneously broadened bands whose spectral positions are shifted as compared to the gas phase. The shifts are caused by interactions with structured solvation shells and the broadenings by fluctuations of these...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics