The Microwave and Millimetre Wave Spectrum, Molecular Constants, Dipole Moment, and Structure of Isocyanic Acid, HNCO

1975 ◽  
Vol 53 (19) ◽  
pp. 1869-1901 ◽  
Author(s):  
W. H. Hocking ◽  
M. C. L. Gerry ◽  
Gisbert Winnewisser
Keyword(s):  
Dipole Moment ◽  
Stark Effect ◽  
Wave Spectrum ◽  
Rotational Constant ◽  
Isocyanic Acid ◽  
Centrifugal Distortion ◽  
Molecular Constants ◽  
Millimetre Wave ◽  
Order Of Magnitude ◽  
First Time

The microwave and millimetre wave spectra of six isotopic species of isocyanic acid, HNCO, have been measured. The molecule is a very slightly asymmetric prolate rotor. Besides the a type R branches, previously reported for two species, we have assigned for the first time a type Q branches and also some intense b type P and R branch transitions. Accurate values of the rotational constants have been determined. The rotational constant A0 is particularly large, with the result that the molecule undergoes very large centrifugal distortion, and terms up to the 12th power in the angular momentum are required to fit the spectrum. 14N nuclear quadrupole hyperfine splitting has been measured and accurate values for both χaa and (χbb − χcc) have been obtained, the latter for the first time. From the Stark effect of the b type transitions we have found the b component of the dipole moment to be 1.35 ± 0.1 D, an order of magnitude larger than previously supposed, and have used it to reinterpret earlier data indicating a variation of the a component with Ka. An improved molecular structure has been obtained. Astrophysical consequences of the large b component of the dipole moment are discussed. A table of transitions of potential astrophysical interest is presented.

Ground state spectroscopic constants and electric dipole moment of D14N12C32S from its microwave and millimetre wave spectra

1978 ◽  
Vol 56 (10) ◽  
pp. 1297-1307 ◽  
Author(s):  
L. B. Szalanski ◽  
M. C. L. Gerry ◽  
G. Winnewisser ◽  
K. Yamada ◽  
M. Winnewisser
Keyword(s):  
Dipole Moment ◽  
Stark Effect ◽  
Coupling Constants ◽  
Spectroscopic Constants ◽  
Wave Spectra ◽  
Centrifugal Distortion ◽  
Millimetre Wave ◽  
Quadrupole Coupling ◽  
Centrifugal Distortion Constants ◽  
First Time

The microwave and millimetre wave spectra of D14N12C32S in its ground vibrational state have been investigated in the frequency region 8–210 GHz. A large number of a-type Q branch and b-type P and R branch transitions up to J = 62 have been assigned and measured for the first time. Their frequencies have been combined with those of the a-type R branches up to K = 5 in an analysis for rotational, centrifugal distortion, and 14N quadrupole coupling constants. Constants obtained, in Watson's S reduction formalism, are: rotational constants in megahertz: A0 = 705 511(370); B0 = 5500.4391(15); C0 = 5445.2252(15); quartic centrifugal distortion constants in kilohertz: Dj = 1.0926(25); Djk = 1333.4(12); d1 = 3.455(5) × 10−2d2 = −7.8(14) × 10−3; 14N quadrupole coupling constants in megahertz: χaa = 1.19(6), χbb−χcc <0.05. The b-component of the dipole moment, μb, has been measured using the Stark effect as 1.08(15) D; this, when combined with μa = 1.67(3) D gives a total dipole moment of 1.99(15) D, essentially parallel to the HN bond.

Millimetre wave spectrum of silyl acetylene in the ground vibrational state

1982 ◽  
Vol 60 (8) ◽  
pp. 1079-1080 ◽  
Author(s):  
J. Carlier ◽  
A. Bauer
Keyword(s):  
Signal Processing ◽  
Vibrational State ◽  
Stark Effect ◽  
Wave Spectrum ◽  
Processing System ◽  
Centrifugal Distortion ◽  
Signal Processing System ◽  
Millimetre Wave ◽  
Ground Vibrational State ◽  
Centrifugal Distortion Constants

The millimetre wave spectrum of silyl acetylene in the ground vibrational state has been observed from 125 to 231 GHz. A new signal processing system using Stark effect has been carried out for the detection of the weakest lines. Refined rotational and centrifugal distortion constants have been derived.

Improved Rotational Constants and Dipole Moment and a Nuclear Quadrupole Coupling Analysis of 2-Cyanothiophene and Dipole Moment of 2-Cyanofurane

1977 ◽  
Vol 32 (2) ◽  
pp. 152-155 ◽  
Author(s):  
J. Wiese ◽  
L. Engelbrecht ◽  
H. Dreizler
Keyword(s):  
Dipole Moment ◽  
Stark Effect ◽  
Dipole Moments ◽  
Quadrupole Coupling Constant ◽  
Rotational Constant ◽  
Coupling Constant ◽  
Frequency Range ◽  
Effect Analysis ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Results of a microwave investigation of the molecules 2-Cyanothiophene and 2-Cyanofurane are reported. The microwave spectrum of 2-Cyanothiophene was examined in the frequency range of 13 -40 GHz mainly to get a more accurate rotational constant A from the assignment of μb-btransitions. From the resolved hyperfine structure due to nuclear quadrupole coupling of the 14N-nucleus the quadrupole coupling constant X+=Xbb + Xcc was determined for 2-Cyanothiophene. No information for X- was available from the measured transitions.From Stark effect studies the dipole moments were determined for both molecules. The nuclear quadrupole coupling as a perturbation of the second order Stark effect was included in the Stark effect analysis

Millimetre wave spectrum of methyl mercaptan

1980 ◽  
Vol 58 (11) ◽  
pp. 1640-1648 ◽  
Author(s):  
R. M. Lees ◽  
M. Ali Mohammadi
Keyword(s):  
Interstellar Medium ◽  
Least Squares ◽  
Wave Spectrum ◽  
Methyl Mercaptan ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Millimetre Wave ◽  
Torsion Vibration ◽  
Vibration Rotation ◽  
Centrifugal Distortion Constants

An investigation of the rotational spectrum of CH332SH, one of the most recent molecules to be detected in the interstellar medium, has been carried out over the 25–107 GHz region. The frequencies of a-type Δk = 0 R-branch transitions have been measured for the J = 1 ← 0 up to J = 4 ← 3 multiplets for torsional states νt = 0–3. In addition, many P-, Q-, and R-branch transitions with Δk ≠ 0 have been identified in order to provide a catalogue of lines for potential radio astronomical applications. Improved values of rotational and centrifugal distortion constants, a-type torsion–vibration–rotation interaction constants, and torsional barrier parameters (V3 = 444.76 cm−1; effective V6 = −2.07 cm−1) have been determined from least-squares analyses of the spectra.

The Microwave Spectrum and Dipole Moment of Hexafluoropropanone

1991 ◽  
Vol 46 (3) ◽  
pp. 229-232 ◽  
Author(s):  
J.-U. Grabow ◽  
N. Heineking ◽  
W. Stahl
Keyword(s):  
Fourier Transform ◽  
Dipole Moment ◽  
Molecular Beam ◽  
Stark Effect ◽  
Microwave Spectrum ◽  
Fourier Transform Spectrometer ◽  
Centrifugal Distortion ◽  
Rotational Constants ◽  
Centrifugal Distortion Constants

AbstractWe recorded the microwave spectrum of hexafluoropropanone between 7 and 15 GHz using a pulsed molecular beam microwave Fourier transform spectrometer. The rotational constants were determined to be A = 2181.71980(14) MHz, B= 1037.22930(7) MHz, C = 934.89233(8) MHz, the quartic centrifugal distortion constants are D'J= 0.07378 (39) kHz, D'JK = 0.10002(75) kHz, D'K = -0.07269(266) kHz, δ'J = 0.00623(29) kHz and R' 6= 0.00755(12) kHz. Stark effect measurements yielded a dipole moment μ = μb= 0.3949 (18) D

Millimetre-wave spectrum of HC17O+. Experimental and theoretical determination of the quadrupole coupling constant of the 17O nucleus

2001 ◽  
Vol 79 (2-3) ◽  
pp. 359-366 ◽  
Author(s):  
L Dore ◽  
C Puzzarini ◽  
G Cazzoli
Keyword(s):  
Wave Spectrum ◽  
Quadrupole Coupling Constant ◽  
Basis Sets ◽  
Coupling Constant ◽  
Centrifugal Distortion ◽  
Millimetre Wave ◽  
Quadrupole Coupling ◽  
Self Consistent Field ◽  
Centrifugal Distortion Constants

The millimetre-wave spectrum of HC17O+ has been analyzed up to 348.2 GHz by recording the J = 2 [Formula: see text] 1 and J = 4 [Formula: see text] 3 rotational transitions. Present measurements and the previous detection of the J = 1 [Formula: see text] 0 transition carried out in this laboratory allowed us to determine accurate values of the rotational and centrifugal distortion constants, and of the nuclear quadrupole coupling (χ) and spin-rotation constants. Moreover, χ has been evaluated from the electric field gradient at the oxygen nucleus calculated by using the multiconfiguration self-consistent field approach plus subsequent multireference configuration interaction computation, employing basis sets of quadruple zeta quality. Excellent agreement with experiment has been obtained. In addition, the molecular dipole moment has been calculated at the same level of accuracy. PACS No.: 33.20Bx

Millimeter-wave spectrum of 3-butynenitrile: Dipole moment and centrifugal distortion constants

1985 ◽  
Vol 114 (1) ◽  
pp. 210-218 ◽  
Author(s):  
J. Demaison ◽  
Ingrid Pohl ◽  
H.D. Rudolph
Keyword(s):  
Dipole Moment ◽  
Millimeter Wave ◽  
Wave Spectrum ◽  
Centrifugal Distortion ◽  
Centrifugal Distortion Constants

scholarly journals First detection of C2H5NCO in the ISM and search of other isocyanates towards the G+0.693-0.027 molecular cloud

2021 ◽  
Vol 654 ◽  
pp. L1
Author(s):  
L. F. Rodríguez-Almeida ◽  
V. M. Rivilla ◽  
I. Jiménez-Serra ◽  
M. Melosso ◽  
L. Colzi ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Isocyanic Acid ◽  
Galactic Centre ◽  
Ethyl Isocyanate ◽  
Excellent Candidate ◽  
Order Of Magnitude ◽  
Density Ratios ◽  
Molecular Abundances ◽  
Spectral Survey ◽  
First Time

Context. Little is known about the chemistry of isocyanates (compounds with the functional group R-N=C=O) in the interstellar medium (ISM), as only four of them have been detected so far: isocyanate radical (NCO), isocyanic acid (HNCO), N-protonated isocyanic acid (H2NCO+), and methyl isocyanate (CH3NCO). The molecular cloud G+0.693-0.027, located in the Galactic Centre, represents an excellent candidate to search for new isocyanates since it exhibits high abundances of the simplest ones, HNCO and CH3NCO. Aims. After CH3NCO, the next most complex isocyanates are ethyl isocyanate (C2H5NCO) and vinyl isocyanate (C2H3NCO). Their detection in the ISM would enhance our understanding of the formation of these compounds in space. Methods. We have searched for C2H5NCO, H2NCO+, C2H3NCO, and cyanogen isocyanate (NCNCO) in a sensitive unbiased spectral survey carried out in the 2 mm and 7 mm radio windows using the IRAM 30m and Yebes 40m radio telescopes, respectively. Results. We have detected C2H5NCO and H2NCO+ towards G+0.693-0.027 (the former for the first time in the ISM) with molecular abundances of (4.7–7.3) × 10−11 and (1.0–1.5) × 10−11, respectively. A ratio of CH3NCO/C2H5NCO = 8 ± 1 is obtained; therefore, the relative abundance determined for HNCO:CH3NCO:C2H5NCO is 1:1/55:1/447, which implies a decrease by more than one order of magnitude, going progressively from HNCO to CH3NCO and to C2H5NCO. This is similar to what has been found for alcohols and thiols, for example, and suggests that C2H5NCO is likely formed on the surface of dust grains. In addition, we have obtained column density ratios of HNCO/NCO > 269, HNCO/H2NCO+ ∼ 2100, and C2H3NCO/C2H5NCO < 4. A comparison of the methyl/ethyl ratios for isocyanates (-NCO), alcohols (-OH), formiates (HCOO-), nitriles (-CN), and thiols (-SH) is performed and shows that ethyl derivatives may be formed more efficiently for the N-bearing molecules than for the O- and S-bearing molecules.

The Micro wave Spectrum of Bromoacetylene ; rs-Structure , Dipole Moment, Quadrupole Coupling Constants and Excited Vibration States

1977 ◽  
Vol 32 (8) ◽  
pp. 866-875 ◽  
Author(s):  
H. Jones ◽  
J. Sheridan ◽  
O. L. Stiefvater
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Stark Effect ◽  
Wave Spectrum ◽  
Normal Modes ◽  
Coupling Constants ◽  
Fermi Resonance ◽  
Bending Vibrations ◽  
Excited Vibration ◽  
Quadrupole Coupling

Abstract The microwave spectrum of bromoacetylene has been investigated in the frequency range from 7 GHz to 35 GHz. From Stark effect measurements the dipole moment has been determined as μ = 0.23 + 0.01 D, and the restructure has been derived in four independent ways from twelve isotopic species: C - H = 1.0553 Å, C ≡ C = 1.2038 Å, C - Br = 1.7913 Å (internal consistency better than ± 0.0003 Å). Quadrupole coupling constants have been determined for eleven isotopic forms and are e q Q = 541.47 MHz and 648.00 MHz for HCCBr81 and HCCBr79, respectively. Rotation spectra have also been observed for excited states of the three lowest normal modes and for several isotopic forms. For the Br81 (Br79) species the rotation-vibration coefficients are α5 = -10.98 (-11.02) MHz, α4 = -1.57 (- 1.61) MHz and α3 = + 12.88 (+ 13.40) MHz. For the bending vibrations, ν5 and ν4 , l-type doubling constants are obtained as ql5 = 4.14 (4.17) MHz and ql4 = 2.6 MHz. Analysis of the Fermi resonance between the first excited state of ν3 and the l = 0 component of the second excited state of ν5 gives the mixing ratio of these two states as a/b = 1.45 (1.51) and the interaction energy as W3,5 = 1.313 (1.181) δ3,5 for the Br81 (Br79) species. With an approximate value of δ3,5 ≌ 25 cm-1, the cubic force constant is obtained as κ3,55 ≌ 44 cm-1.The results are discussed in relation to the molecular properties of other halogen acetylenes and halogen cyanides.

Infrared spectrum of the fundamental ν1 of deutero-isocyanic acid

1981 ◽  
Vol 59 (10) ◽  
pp. 1313-1326 ◽  
Author(s):  
D. A. Steiner ◽  
S. R. Polo ◽  
T. K. McCubbin Jr. ◽  
K. A. Wishah
Keyword(s):  
High Resolution ◽  
Infrared Spectrum ◽  
Isocyanic Acid ◽  
Centrifugal Distortion ◽  
Rotational Constants ◽  
Fundamental Band ◽  
Band Origin ◽  
Stretching Vibration ◽  
Centrifugal Distortion Constants ◽  
First Time

The ν1 fundamental band of DNCO has been observed for the first time under high resolution. The band origin for this deuterium–nitrogen stretching vibration is found to be at 2637.198 cm−1, rather distant from the previously reported value of 2634.9 cm−1. Eighteen subbands have been analyzed and term values for both ground and ν1 states with K up to 6 have been obtained. Effective rotational constants Bν and centrifugal distortion constants Dν and Hν have also been determined. Interaction is observed with the 2ν3 vibration which has a band origin around 2640 cm−1. Interesting perturbations are observed for the K = 0 and K = 4 levels of ν1.

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