scholarly journals The Other Rotamer of Formic Acid, cis-HCOOH1

1976 ◽  
Vol 31 (9) ◽  
pp. 1113-1121 ◽  
Author(s):  
William H. Hocking
Keyword(s):  
Formic Acid ◽  
Stark Effect ◽  
Energy Difference ◽  
Energy Curve ◽  
Rotational Spectrum ◽  
Vibrational States ◽  
Intensity Measurements ◽  
Centrifugal Distortion Constants ◽  
Cis And Trans ◽  
First Time

Abstract The rotational spectrum of the planar cis rotamer of formic acid, cis-HCOOH, has been detected for the first time. Twenty transitions belonging to the qRK, qQ1, qQ2 , rP0 , rP1,rP2 branches of the parent isotopic species in its ground state have been assigned and measured. The rotational constants and quartic centrifugal distortion constants have been determined using Watson's reduced Hamiltonian. Stark effect measurements have yielded the molecular electric dipole moment: μa= 2.65(1) D, μb = 2.71(1) D and , μ= 3.79(1) D. The energy difference between the ground vibrational states of cis-and trans-HCOOH has been determined by microwave relative intensity measurements. The cis rotamer is found to lie at higher energy than the trans rotamer by 1365 ± 30 cm-1 . A one dimensional potential energy curve has been calculated for the OH torsional vibration of formic acid.

The Rotational Spectrum of Monothioformic Acid. III. Dipole Moment and Relative Intensity Measurements1,2

1976 ◽  
Vol 31 (8) ◽  
pp. 995-1001 ◽  
Author(s):  
William H. Hocking ◽  
Gisbert Winnewisser
Keyword(s):  
Dipole Moment ◽  
Relative Intensity ◽  
Electric Dipole ◽  
Ground State ◽  
Stark Effect ◽  
Energy Difference ◽  
Rotational Spectrum ◽  
Vibrational States ◽  
Intensity Measurements ◽  
Cis And Trans

Abstract The molecular electric dipole moment of each of the two planar thiol rotamers of monothio-formic acid, in its ground state, has been determined from Stark effect measurements. The results are for cis-HC(:O)SH: μa=1.805(1) D, μb = 2.228(1) D and μ=2.868(1) D; whereas for trans-HC(:O)SH: μa = 1.366(1) D, μb = 0.702(1) D and μ = 1.536(1) D. Additional Stark effect measurements on HC(:O)SD and DC(:O)SH have yielded the direction of the dipole moment in each rotamer. The energy difference between the ground vibrational states of cis-and trans-HC(:O)SH has also been determined by relative intensity measurements. The cis rotamer is found to lie at higher energy than the trans rotamerb y 2767(7) J·mol-1 (231.3(6) cm-1 or 661.3(17) cal·mol-1).

The Rotational Spectrum of Monothioformic Acid. I. cis-and trans-HC(:O)SH1,2

1976 ◽  
Vol 31 (5) ◽  
pp. 422-437
Author(s):  
William H. Hocking ◽  
Gisbert Winnewisser
Keyword(s):  
Frequency Region ◽  
Absorption Lines ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Astrophysical Interest ◽  
Rotational Spectra ◽  
Measured Line ◽  
Centrifugal Distortion Constants ◽  
Cis And Trans ◽  
Line Positions

Abstract The rotational spectra of the two abundant isomers of monothioformic acid, cis- and trans- HC(:O)SH, have been assigned in the frequency region 8 -250 GHz. Over 90 a-type transitions and over 60 b-type transitions have been measured for each rotamer. The a-type transitions belong to the qRK , qQ1, qQ2, qQ3 and qQ4 branches and the b-type absorption lines encompass the Ka = 1 - 0, 2 - 1, 3 - 2, 4 - 3 and 5 - 4 rotational sub-bands. The rotational constants and all quartic and sextic centrifugal distortion constants have been determined for each rotamer using Watson's reduced Hamiltonian. In addition to the measured line positions the frequencies of some selected low-J transitions, not observed in this work but of potential astrophysical interest, have been listed as an aid in the interstellar search for monothioformic acid.

The Centrifugally Induced Pure Rotational Spectrum and the Structure of Sulfur Trioxide. A Microwave Fourier Transform Study of a Nonpolar Molecule

1991 ◽  
Vol 46 (8) ◽  
pp. 710-714 ◽  
Author(s):  
Volker Meyer ◽  
Dieter Hermann Sutter ◽  
Helmut Dreizler
Keyword(s):  
Fourier Transform ◽  
Sulfur Trioxide ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Rotational Constants ◽  
Nonpolar Molecule ◽  
Centrifugal Distortion Constants ◽  
First Time

AbstractThe pure rotational spectrum of sulfur trioxide has been observed for the first time. A total of 25 high-J transitions could be assigned. The rotational constants, two quartic centrifugal distortion constants, and three sextic centrifugal distortion constants were determined as: B= 10 449.0667(23) MHz, C = 5216.0330(12) MHz, DJ = 9.2651 (18) kHz, DJK = -16.3922(18) kHz, HJ, = -8.8(34) • 10-3 Hz, HJK= -15.8(73) • 10-3 Hz, and HKJ = 34.2(73) • 10-3 Hz. An r0- and an re -structure are presented: r0= 1.4198(7) Å (calculated from B), r0 = 1.4210(7) Å (calculated from C), and re = 1.4175 Å

scholarly journals Accurate rest frequencies for propargylamine in the ground and low-lying vibrational states

2018 ◽  
Vol 615 ◽  
pp. A176 ◽  
Author(s):  
C. Degli Esposti ◽  
L. Dore ◽  
C. Puzzarini ◽  
M. Biczysko ◽  
J. Bloino ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Organic Molecules ◽  
Coupling Constants ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Vibrational States ◽  
Important Species ◽  
Centrifugal Distortion Constants ◽  
High Level

Context. To date, several complex organic molecules have been detected in the interstellar medium, and they have been suggested as precursors of biologically important species. Propargylamine (HC ≡C−CH2−NH2) is structurally similar to a number of other organic molecules which have already been identified by radioastronomy, making it a good candidate for astrophysical detection. Aims. This work provides accurate rest frequencies of propargylamine, from the centimeter-wave to the submillimeter-wave region, useful to facilitate the detection of this molecule in the interstellar medium. Methods. An extensive laboratory study of the rotational spectrum of propargylamine has been performed using a pulsed-jet Fourier Transform Microwave (FTMW) spectrometer (7–19 GHz frequency range) and a frequency modulation microwave spectrometer (75–560 GHz). Several hundred rotational transitions of propargylamine were recorded in the ground and three lowest excited vibrational states. The experiments were supported by high-level ab initio computations, mainly employed to characterize the vibrational state structure and to predict spectroscopic parameters unknown prior to this study. Results. The measured transition frequencies yielded accurate rotational constants and the complete sets of quartic and sextic centrifugal distortion constants for propargylamine in its vibrational ground state. 14N-nuclear quadrupole coupling constants were also determined. Rotational and quartic centrifugal distortion constants were also obtained for the low-lying excited states v13 = 1 (A′), v20 = 1 (A″), and v21 = 1 (A″). The a-type Coriolis resonance which couples the v13 = 1 and v21 = 1 levels was analyzed. Conclusions. The determined spectroscopic constants allowed for the compilation of a dataset of highly accurate rest frequencies for astrophysical purposes in the millimeter and submillimeter regions with 1σ uncertainties that are smaller than 0.050 MHz, corresponding to 0.03 km s−1 at 500 GHz in radial equivalent velocity.

Rotational Spectrum , Electric Dipole Moment, Quadrupole Coupling , and Partial r0- Structure of 3 -Cyanothiophene

1977 ◽  
Vol 32 (8) ◽  
pp. 890-896 ◽  
Author(s):  
J. Wiese ◽  
D. H. Sutter
Keyword(s):  
Dipole Moment ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Stark Effect ◽  
Quadrupole Coupling Constant ◽  
Abundant Species ◽  
Rotational Spectrum ◽  
Quadrupole Coupling ◽  
Centrifugal Distortion Constants ◽  
Ring Distortion

Abstract The microwave rotational spectrum of the most abundant species of 3-Cyanothiophene was investigated for the ground vibrational state. Rotational constants and centrifugal distortion constants are given. The electric dipole moment components μa and μb and the 14N-quadrupole coupling constant X + = X bb + X cc were determined from the Stark-effect splittings and hfs-splittings respectively. The experimental results are compared to CNDO/2 calculations and are discussed with reference to ring distortion.

The Rotational Spectrum of Monothioformic Acid. II. cis-and trans-HC(:O)SD, DC(:O)SH, HC(:O)34 SH1,2

1976 ◽  
Vol 31 (5) ◽  
pp. 438-453
Author(s):  
William H. Hocking ◽  
Gisbert Winnewisser
Keyword(s):  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Rotational Constants ◽  
Rotational Spectra ◽  
Centrifugal Distortion Constants ◽  
Cis And Trans

Abstract The rotational spectra of three isotopically substituted species of monothioformic acid, DCOSH, HCOSD, HCO34SH, have been investigated. Transitions arising from two different isomeric forms have been observed in each instance. Rotational constants and quartic centrifugal distortion constants have been determined for all species using Watson’s reduced Hamiltonian. It has been established that the two abundant isomers of monothioformic acid are the planar cis and trans thiol rotamers. The structure of cis-HC ( :O ) SH is found to be: r ( C - H ) =1.100 Å, r ( S - H ) =1.336 Å, r ( C - S ) =1.771 Å, r(C=0) =1.210 Å, ∢(OCS) =122.4°, ∢(HSC) =94.7° and ∢(HCS) = 114.6°; whereas for trans-HC ( :O ) SH: r(C - H ) =1.100 Å, r (S - H) =1.351 Å, r (C - S) = 1.763 Å, r(C=O) = 1.218 Å, ∢(OCS) =126.0°, ∢(HSC) = 92.7 ° and ∢(HCS) =111.8°.

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.

Mikrowellenspektrum, Hinderungspotential der internen Rotation und Dipolmoment des meta-Fluortoluols

1968 ◽  
Vol 23 (1) ◽  
pp. 68-76 ◽  
Author(s):  
Heinz Dieter Rudolph ◽  
Axel Trinkaus
Keyword(s):  
Dipole Moment ◽  
Spectral Data ◽  
Internal Rotation ◽  
Benzene Ring ◽  
Stark Effect ◽  
Rotational Spectrum ◽  
Symmetrical Potential ◽  
First Time ◽  
Comparable Magnitude ◽  
Potential Parameters

The rotational spectrum of meta-fluorotoluene has been measured in the four lowest states of internal rotation of the methyl top m = 0, 1, 2, 3. The rotational constants obtained for m = 0 are A = 3715,2, B = 1766,51, C = 1197,58 MHz. The barrier hindering internal rotation is very low. For the first time threefold and sixfold-symmetrical potential components V3 and V6 of comparable magnitude have been found. This appears to be plausible in view of the fact that for this molecule the bond geometrical asymmetry responsible for V3 (meta substituent) is much more distant from the CH3-group than the local C2v-symmetry of the benzene ring causing V6. Fitting V3 and V6 to the spectral data one cannot discriminate between two possible sets of potential parameters which differ by the sign of V6 and, to a lesser extent, by the magnitude of V3 and V6: set I: V3 = 45,3, V6V6 = + 22,8, set II: V3 = 48,4, V6 = — 15,1 cal/mole. The reason for the sign remaining effectively indeterminate although physically relevant in connection with the shape of the barrier is discussed. — The dipole moment components derived from Stark-effect measurements are μα = 1,71, μb = 0,62 D.

Microwave spectrum of methylthioacetonitrile

1978 ◽  
Vol 56 (6) ◽  
pp. 772-776 ◽  
Author(s):  
R. Kewley
Keyword(s):  
Microwave Spectrum ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Frequency Range ◽  
Gauche Conformer ◽  
Intensity Measurements ◽  
Trans Conformer ◽  
Microwave Rotational Spectrum ◽  
Torsional Frequency ◽  
Centrifugal Distortion Constants

The microwave rotational spectrum of methylthioacetonitrile has been studied in the frequency range 18–37 GHz. The spectrum found is that of the gauche conformer. The non-observation of the spectrum of the trans conformer indicates that its abundance is less than about 5%. The rotational and centrifugal distortion constants for the ground vibrational state of the gauche conformer are: A = 7715.123 MHz, B = 2641.756 MHz, C = 2174.538 MHz, DK = 0.6824 MHz, DJK = −2.52 kHz, and DJ = 1.96 kHz. The observed rotational constants are compatible with a dihedral angle of 66 ± 5° and a CSC angle of 104 ± 2°. The dipole moment of the gauche conformer has been determined as 3.02 D. Vibrational satellites due to S—CH2 torsion have been observed and a torsional frequency of 101 cm−1 has been estimated from relative intensity measurements.

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