Rotational spectrum and tentative detection of DCOOCH3–Methyl formate in Orion

New centimeter-wave (7–80 GHz) and submillimeter-wave (580–661 GHz) spectra of a deuterated species of methyl formate (DCOOCH3) have been measured. Transitions with a maximum value of J = 64 and K = 36 have been assigned and fitted together with previous measurements. The internal rotation of this compound was treated using the so-called rho axis method. A total of 1703 transitions were fitted using this method. Only 24 parameters were employed in the final fit, which has an rms deviation of 94.2 kHz. The dipole moment and the nuclear quadrupole coupling constants of the deuterated specie have also been obtained. This new study has permitted a tentative detection of DCOOCH3 in Orion with the IRAM 30 m telescope based on the observation of more than 100 spectral features with low blending effects among the 400 lines expected in the observed frequency domain (for which over 300 are heavily blended with other species). These 100 transitions are above noise and confusion limited without heavy blending and cannot be assigned to any other species. Moreover, none of the strongest unblended transitions is missing. The derived source-averaged total column density for DCOOCH3 is 7.8 × 1014 cm−2 and theDCOOCH3/HCOOCH3 column density ratio varies between 0.02 and 0.06 in the different cloud components of Orion. This value is consistent with the deuteration enhancement found for other species in this cloud

Rotational spectrum of ethyl cyanoacetylene (C

Context. New radiotelescopes, such as the very sensitive ALMA, will enable the detection of interstellar molecules in much lower concentrations than previously possible. A successful identification of an interstellar molecule requires that laboratory microwave and millimeter-wave spectra are investigated. Several cyanopolyynes and alkynylcarbonitriles have already been detected in the interstellar medium (ISM). Cyanoacetylene (HC≡C–C≡N) is abundant in the ISM and its methyl derivative, 2-butynenitrile (CH3C≡C–C≡N), is also present. The next derivative, ethyl cyanoacetylene, (2-pentynenitrile C2H5C≡C–C≡N) may also be present in interstellar space. Aims. We report the rotational spectrum of the ethyl cyanoacetylene (C2H5C≡C–C≡N). This is hoped to facilitate identifying gaseous ethyl cyanoacetylene in the ISM. Methods. We studied the rotational spectrum of C2H5C≡C–C≡N between 13 and 116 GHz with the microwave spectrometer of the University of Oslo. The spectroscopic study was augmented by high-level quantum-chemical calculations at B3LYP/cc-pVTZ and CCSD/cc-pVTZ levels of theory. Results. We present for the first time the rotational spectrum of the ethyl cyanoacetylene (C2H5C≡C–C≡N). We assigned 342 transitions of the vibrational ground state, accurate values were obtained for rotational and centrifugal distortion constants, and the dipole moment was determined as well