The millimeter-wave spectrum of diketene, (CH2CO)2, was obtained at room temperature in the frequency range of 260-360 GHz. Theoretical predictions of the vibration-rotation interactions were computed at the CCSD(T)/ANO1 level using an anharmonic frequency calculation in CFOUR. The spectra of the ground state of diketene, ν24, and 2ν24 have been observed in this investigation and were previously reported by Mönnig, et al. in the m-wave region.1 Vibrational state ν24 is the lowest energy vibrational state (fundamental frequency 129 cm-1) corresponding to a ring deformation. To extend the investigation of the ν24 vibrational states, a large number (&gt;1400) of spectral lines of 3ν24 were assigned and fit to an experimental accuracy of s = 0.045 using an S-reduced Hamiltonian in the Ir representation. The large number of measured transitions allowed the fitting of the rotational constants and all quartic and sextic centrifugal distortion coefficients. Study of the pure rotational spectrum of diketene in the ground vibrational state and the excited vibrational states is important preliminary work for attempts to measure and assign the spectrum of acylium cation (CH3CO+). As the methylated analog of HCO+, we are hopeful that transitions detected for acylium cation will be of astrochemical relevance and lead to its detection in the interstellar medium. 1. Mönnig, F.; Dreizler, H.; Rudolph, H. D., Rotationsspektrum, Konfiguration, Dipolmoment und Ring-Deformationsschwingung von Diketen. Z. Naturforsch., A: Phys. Sci. 1967, 22, 1471-1473.

Millimeter-wave spectroscopy of diketene: Determination of the rotational constants for the third quantum vibration (ν24)

251st National Meeting (2016)

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