scholarly journals The millimeter-wave spectrum and astronomical search for ethyl methyl sulfide

2020 ◽  
Vol 639 ◽  
pp. A129
Author(s):  
C. Cabezas ◽  
C. Bermúdez ◽  
B. Tercero ◽  
J. Cernicharo
Keyword(s):  
Internal Rotation ◽  
Excited States ◽  
Millimeter Wave ◽  
Wave Spectrum ◽  
Potential Candidate ◽  
Rotational Spectrum ◽  
Methyl Sulfide ◽  
Ethyl Methyl ◽  
Abundant Element ◽  
High Level

Context. Sulfur-containing molecules constitute only 8% of the molecules observed in the interstellar medium (ISM), in spite of the fact that sulfur has been shown to be an abundant element in the ISM. In order to understand the chemical behavior of the ISM and specific cases like the missing sulfur reservoir, a detailed chemical molecular composition in the ISM must be mapped out. Aims. Our goal is to investigate the rotational spectrum of ethyl methyl sulfide, CH3CH2SCH3, which seems to be a potential candidate for observation in the ISM since the simpler analogs, CH3SH and CH3CH2SH, have already been detected. Rotational spectrum of ethyl methyl sulfide has been observed before, but its experimental rotational parameters are not precise enough to allow its detection in the ISM. Methods. The rotational spectrum of ethyl methyl sulfide in the frequency range 72−116.5 GHz was measured using a broadband millimeter-wave spectrometer based on radio astronomy receivers with fast Fourier transform backends. The spectral searches and identification of the vibrational excited states of ethyl methyl sulfide was supported by high-level ab initio calculations on the harmonic and anharmonic force fields. Results. The rotational spectra for the trans and gauche conformers of ethyl methyl sulfide was analyzed, and a total of 172 and 259 rotational transitions were observed for each one, respectively. The observation of A − E internal rotation splittings allowed the experimental determination of the V3 hindered internal rotation barrier height for both trans and gauche species. In addition, the vibrational excited states, resulting from the lowest frequency vibrational mode ν30 were identified for both conformers. The new experimental rotational parameters were employed to search for ethyl methyl sulfide in the warm and cold molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30 m at 3 mm and 2 mm.

scholarly journals The millimeter-wave spectrum and astronomical search of succinonitrile and its vibrational excited states

2019 ◽  
Vol 629 ◽  
pp. A35 ◽  
Author(s):  
C. Cabezas ◽  
C. Bermúdez ◽  
J. D. Gallego ◽  
B. Tercero ◽  
J. M. Hernández ◽  
...  
Keyword(s):  
Excited States ◽  
Millimeter Wave ◽  
Dipole Moments ◽  
Saturated Hydrocarbon ◽  
Wave Spectrum ◽  
Rotational Spectrum ◽  
Rotational Spectra ◽  
Quantum Numbers ◽  
Centrifugal Distortion Constants ◽  
High Level

Context. Dinitriles with a saturated hydrocarbon skeleton and a −C≡N group at each end can have large electric dipole moments. Their formation can be related to highly reactive radicals such as CH2CN, C2N, or CN. Thus, these saturated dinitriles are potential candidates to be observed in the interstellar medium (ISM). Aims. Our goal is the investigation of the rotational spectrum of one of the simplest dinitriles N≡C−CH2−CH2−C≡N, succinonitrile, whose actual rotational parameters are not precise enough to allow its detection in the ISM. In addition, the rotational spectra for its vibrational excited states will be analysed. Methods. The rotational spectra of succinonitrile was measured in the frequency range 72−116.5 GHz 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. Results. 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, resulting from the four lowest frequency vibrational modes ν13, ν12, ν24, and ν23 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 30 m at 3 mm and the Yebes 40 m at 1.3 cm and 7 mm.

Millimeter-Wave Spectrum of Ethyl Formate

1984 ◽  
Vol 39 (6) ◽  
pp. 560-564 ◽  
Author(s):  
J. Demaison ◽  
D. Boucher ◽  
J. Burie ◽  
A. Dubrulle
Keyword(s):  
Internal Rotation ◽  
Millimeter Wave ◽  
Wave Spectrum ◽  
Ethyl Formate ◽  
Rotational Spectrum ◽  
Kcal Mole ◽  
Methyl Group

The rotational spectrum of ethyl formate has been investigated up to 240 GHz. High J transitions of both a-type and b-type have been measured for the two isomers and fitted to a centrifugally distorted Hamiltonian including some sextic coefficients. The results of the analysis are sufficiently accurate for the prediction of all strong transitions throughout the millimeterwave range. No splitting due to the internal rotation of the methyl group was observed, which indicates that the barrier to internal rotation is of the order of 3 kcal/mole or greater.

Millimeter-Wave Spectrum of Ethyl Acetylene Centrifugal Distortion, Coriolis Interaction and Internal Rotation

1983 ◽  
Vol 38 (4) ◽  
pp. 447-451 ◽  
Author(s):  
J. Demaison ◽  
D. Boucher ◽  
J. Burie ◽  
A. Dubrulle
Keyword(s):  
Excited State ◽  
Internal Rotation ◽  
Plane Deformation ◽  
Wave Spectrum ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Coriolis Interaction ◽  
Methyl Group ◽  
First Excited State ◽  
Methyl Torsion

The rotational spectrum of ethyl acetylene has been investigated between 70 and 320 GHz. A Coriolis interaction has been found between the first excited state of the methyl torsion and the C - C = C in plane deformation. Splittings of transitions in the first excited torsional state show that the barrier hindering internal rotation of the methyl group amounts to 3271 cal/mole.

scholarly journals The millimeter-wave spectrum of methyl ketene and the astronomical search for it

2018 ◽  
Vol 619 ◽  
pp. A92 ◽  
Author(s):  
C. Bermúdez ◽  
B. Tercero ◽  
R. A. Motiyenko ◽  
L. Margulès ◽  
J. Cernicharo ◽  
...  
Keyword(s):  
Excited State ◽  
Millimeter Wave ◽  
Ground State ◽  
Wave Spectrum ◽  
High Mass ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions

Context. The analysis of isomeric species of a compound observed in the interstellar medium (ISM) is a useful tool to understand the chemistry of complex organic molecules. It could, likewise, assist in the detection of new species. Aims. Our goal consists in analyzing one of the two most stable species of the C3H4O family, methyl ketene, whose actual rotational parameters are not precise enough to allow its detection in the ISM. The obtained parameters will be used to search for it in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark clouds TMC-1 in the Taurus Molecular Cloud and Barnard 1 (B1–b). Methods. A millimeter-wave room-temperature rotational spectrum of methyl ketene was recorded from 50 to 330 GHz. The internal rotation analysis of its ground state and first torsional excited state was performed with the rho-axis method employing the RAM36 program. Results. More than 3000 transitions of the rotational spectrum of the ground state (Kamax = 18) and first torsional excited state (Kamax = 13) of methyl ketene were fitted using a Hamiltonian that contains 41 parameters with a root mean square of 44 kHz. Column density limits were calculated but no lines were detected in the ISM belonging to methyl ketene.

scholarly journals Mikrowellenspektrum, Hinderungspotential der internen Rotation, Quadrupolkopplungskonstanten und Dipolmoment des 2-Methyl-Pyridins

1970 ◽  
Vol 25 (1) ◽  
pp. 25-35 ◽  
Author(s):  
H. Dreizler ◽  
H.D. Rudolph ◽  
H. Mäder
Keyword(s):  
Dipole Moment ◽  
Hyperfine Structure ◽  
Internal Rotation ◽  
Excited States ◽  
Stark Effect ◽  
Coupling Constants ◽  
Rotational Spectrum ◽  
Microwave Rotational Spectrum ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Abstract The microwave rotational spectrum of 2-methyl-pyridine (a-picoline) has been investigated in the region from 6 to 30 kmc/s. From the three lowest states of internal rotation m=0, 1, 2 the three-and sixfold components V3 and V6 of the potential barrier hindering the internal rotation have been determined to be V3= (258,4 ± 0,1) cal/mole and V6=(-11,8± 0,1) cal/mole. From the splitting of low-J lines m=0 the nuclear quadrupole coupling constants for the 14N nucleus have been derived as χaa= (-0,33 ± 0,02) mc/s, χbb = (-2,86 ± 0,02) mc/s, χcc = (+3,19 ± 0,02) mc/s. The hyperfine structure of rotational transitions in excited states of internal rotation could also be accounted for with these coupling constants. The dipole moment components derived from Stark-effect measurements in the ground torsional state m = 0 are μa = (0,72 ± 0,01) Debye and μb - (1,71 ± 0,02) Debye.

scholarly journals Millimeter-Wave Rotational Spectrum, Barrier to Internal Rotation, and DFT Calculation of o-Tolunitrile

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
A. I. Jaman ◽  
P. Hemant Kumar ◽  
P. R. Bangal
Keyword(s):  
Internal Rotation ◽  
Millimeter Wave ◽  
Dft Calculation ◽  
Rotational Spectrum ◽  
Frequency Range ◽  
Rotational Spectra ◽  
Calculation Results ◽  
Rotation Parameters ◽  
Experimental Values

The millimeter-wave rotational spectra of o-tolunitrile (C6H4CH3CN) have been investigated in the ground torsional state in the frequency range 50.0–75.0 GHz. Many high-J rotational lines with large A-E splitting due to internal rotation of the methyl top have been assigned. A least squares analysis of the A-E splitting of 92 transitions resulted in the determination of accurate values of internal rotation parameters. The observed parameters were compared with the previously reported experimental values and DFT calculation results.

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