Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

The Rotational Spectra Structure, Internal Dynamics and Electric Dipole Moment of Argon-Ketene Van Der Walls Complex



C W. Gillies, J Z. Gillies, S J. Amadon, R D. Suenram, Francis J. Lovas, H Warner, R Malloy


Pulsed-beam Fourier transform microwave spectroscopy was used to observe and assign the rotational spectra of the argon-ketene van der Waals complex. Tunneling of the hydrogen or deuterium atoms splits the a- and b-type rotational transitions of H2CCO-Ar, H2C13CCO-Ar H2C13CO-Ar, and D2CCO-Ar into two states. This internal motion appears to be quenched for HDCCO-Ar where only one state is observed. The spectra of all isotopomers were satisfactorily fit to a Watson asymmetric top Hamiltonian which gave A = 10447,9248(10) MHz, B= 1918.0138(16) MHz, C = 1606.7642(15) MHz, δj = 16.0856(70) kHz, δ k = -152.24(23) kHz, δj = 2.5313(18) kHz, δk = 209.85(82) kHz, and hk = 1.562 (64) kHz for the A1 state of H2CCO-Ar. Electric dipole moment measurements determined a = 0.417(10)x10-30 C m [0.125(3)D] and b = 4.566 (7) x 10-30 C m [1.369(2)D] along the a and b principal axes of the A1 state of the normal isotopomer. A least squares fit of principal moments of inertia, Ia and Ic, of H2CCO-Ar, H2 13CCO-Ar, H2C13CO-Ar, and D2CCO-Ar for the A1 states give the argon-ketene center of mass separation, Rcm = 3.589 (1) and the angle between the line connecting argon with the center of mass of ketene and the C=C=O axis, θcm = 83.3 (6). The spectral data are consistent with a planar geometry and the argon atom is tilted toward the methylene carbon of ketene by 6.7 from a T-shaped configuration.
Journal of Molecular Spectroscopy


Argon-ketene, Fourier-transform spectrum, microwave, molecular structure, rotational spectrum, spectra, van der Waals complex


Gillies, C. , Gillies, J. , Amadon, S. , Suenram, R. , Lovas, F. , Warner, H. and Malloy, R. (2001), The Rotational Spectra Structure, Internal Dynamics and Electric Dipole Moment of Argon-Ketene Van Der Walls Complex, Journal of Molecular Spectroscopy (Accessed June 21, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created May 31, 2001, Updated October 12, 2021