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Description
Dinitriles with a saturated hydrocarbon skeleton and a -CN group at each end can have large electric dipole moments. Their formation can be related to highly reactive radicals such as CH_2_CN, C_2_N or CN. Thus, these saturated dinitriles are potential candidates to be observed in the ISM. Our goal is the investigation of the rotational spectrum of one of the simplest dinitriles NC-CH_2_-CH_2_-CN, succinonitrile, whose actual rotational parameters are not precise enough to allow its detection it in the ISM. In addition, the rotational spectra for its vibrational excited states will be analyzed. The rotational spectra of succinonitrile was measured in the frequency range 72-116.5GHz using a new broadband millimeter-wave spectrometer based on radio astronomy receivers with Fast Fourier Transform backends. The identification of the vibrational excited states of succinonitrile was supported by high-level ab initio calculations on the harmonic and anharmonic force fields. A total of 459 rotational transitions with maximum values of J and Ka quantum numbers 70 and 14, respectively, were measured for the ground vibrational state of succinonitrile. The analysis allowed us to accurately determine the rotational, quartic and sextic centrifugal distortion constants. Up to eleven vibrational excited states, resulted from the four lowest frequency vibrational modes nu13, nu12, nu24 and nu23 were identified. In addition to the four fundamental modes, we observed overtones together with some combination states. The rotational parameters for the ground state were employed to unsuccessfully search for succinonitrile in the cold and warm molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1,using the spectral surveys captured by IRAM 30m at 3mm and the Yebes 40m at 1.3cm and 7mm.
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