The ν4 Vibration–Rotation Bands of C6H6 and C6D6: The Analysis of the Bands and the Determination of the Bond Lengths

1974 ◽  
Vol 52 (20) ◽  
pp. 1949-1955 ◽  
Author(s):  
A. Cabana ◽  
J. Bachand ◽  
J. Giguère
Keyword(s):  
High Resolution ◽  
Ground State ◽  
Spectroscopic Constants ◽  
Vibrational States ◽  
Rotational Constants ◽  
Bond Lengths ◽  
Vibration Rotation

The ν4. vibration–rotation bands of benzene and benzene-d6 have been recorded with high resolution. The K = 0 subbands have been analyzed and spectroscopic constants for both vibrational states have been calculated. Assuming D6h symmetry for the molecules the bond lengths have been determined from the ground state rotational constants of the two isotopic molecules. The values obtained are: r0(C—C) = 139.64 ± 0.02 pm and r0(C—H) = 108.31 ± 0.13 pm.

Vibration-rotation bands of monodeuteroacetylene and the molecular dimensions

1956 ◽  
Vol 234 (1198) ◽  
pp. 306-317 ◽  
Keyword(s):  
High Resolution ◽  
Ground State ◽  
Fermi Resonance ◽  
Rotational Constants ◽  
Bond Lengths ◽  
Vibrational Levels ◽  
Vibration Rotation ◽  
Molecular Dimensions

Some vibration-rotation bands of monodeuteroacetylene have been measured with high resolution. Values have been derived for the coefficients α i relating the rotational constants in different vibrational levels, as follows: α 2 = + 0⋅00439, α 3 = + 0⋅00638, α 4 = — 0⋅0032 2 , α 5 = — 0⋅0011. Using the value B 00000 = 0⋅9910 5 cm -1 , also determined from many bands, a new value, B e = 0⋅9948, has been obtained leading to new estimates for the bond lengths r e CH = 1⋅058 Å, and r e C≡C = 1⋅205 0 . The l -doubling coefficient has been determined in two states, namely, q 00010 = 0⋅0056 and q 00003 = 0⋅0072. In the ground state the results are in accordance with a centrifugal stretching coefficient D = 0⋅7 x 10 -6 , but in some higher levels a markedly different value is derived, which may, however, arise through the effects of Fermi resonance.

High-resolution Raman spectroscopy of gases and the determination of molecular bond lengths

2000 ◽  
Vol 78 (5-6) ◽  
pp. 327-390 ◽  
Author(s):  
W J Jones
Keyword(s):  
Raman Spectroscopy ◽  
High Resolution ◽  
Bond Length ◽  
Subsequent Development ◽  
Bond Lengths ◽  
Pure Rotation ◽  
Wide Range ◽  
Laser Sources ◽  
Vibration Rotation

This review highlights the developments that have taken place in the field of high-resolution Raman spectroscopy of gases from the pioneering studies of Stoicheff and Welsh in the early fifties to the present day. This period has seen major changes in the methods that have been employed for investigating pure rotation and vibration-rotation spectra from these initial studies with Hg excitation through to the deployment of laser sources for incoherent Raman scattering at enhanced sensitivity, and the subsequent development of the techniques of nonlinear Raman spectroscopy at resolutions of ~10-3 cm-1. A central theme in this review is the measurement of accurate rotational constants for nonpolar molecules that have then been employed for the determination of molecular geometries and bond lengths. The studies by Stoicheff of the pure rotational spectra of a wide range of linear and symmetric-top molecules provided an extensive data base that served to supplement bond-length determinations from other methods and enabled him to correlate CC and CH bond length variations in noncyclic compounds with changes in their environment. The discovery of laser sources in the sixties provided exciting new opportunities for the examination of pure rotation and vibration-rotation spectra at enhanced resolution and sensitivity and broadened dramatically the scope of the field. Apart from the improvements in the incoherent scattering methods afforded by these new sources, the discovery of a range of new nonlinear Raman phenomena, a field in which Stoicheff made equally important contributions, led to the creation of a range of new coherent nonlinear Raman methods that have been widely employed for the study of all rotor classes. Representative examples of the many investigations performed with the various spectroscopic methods over this period are given, together with the results of the structure determinations achieved from the analyses of the rotational spectra.PACS Nos.: 33.20Fb, 36.20.Hb

HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: XIII. ROTATIONAL SPECTRA AND STRUCTURES OF THE ZINC-, CADMIUM-, AND MERCURY-DIMETHYL MOLECULES

1960 ◽  
Vol 38 (11) ◽  
pp. 1516-1525 ◽  
Author(s):  
K. Suryanarayana Rao ◽  
B. P. Stoicheff ◽  
R. Turner
Keyword(s):  
Raman Spectroscopy ◽  
High Resolution ◽  
Rotational Constants ◽  
Carbon Bond ◽  
Rotational Spectra ◽  
Bond Lengths ◽  
Zinc Cadmium ◽  
Symmetric Top Molecules

The pure rotational spectra of gaseous Zn(CH3)2, Cd(CH3)2, Hg(CH3)2, and of the fully deuterated molecules have been photographed with a 21-ft grating. The spectra are typical of symmetric top molecules and consist of many evenly spaced rotational lines having a separation of about 0.45 cm−1. An analysis of the spectra yielded the rotational constants (in cm−1)[Formula: see text]From these constants the following metal—carbon bond lengths were determined: Zn—C = 1.929 Å, Cd—C = 2.112 Å, and Hg—C = 2.094 Å. Relations for the C—H bond lengths and HCH angles were also obtained.

Vibration-rotation bands and rotational constants of dideuteroacetylene

1955 ◽  
Vol 232 (1190) ◽  
pp. 291-309 ◽  
Keyword(s):  
Resolving Power ◽  
Vibrational States ◽  
Absorption Bands ◽  
Rotational Constants ◽  
Vibrational Assignments ◽  
Vibrational Anharmonicity ◽  
A Value ◽  
Vibrational Levels ◽  
Vibration Rotation ◽  
Very High

Nine vibrational absorption bands of dideutero-acetylene have been examined with very high resolving power. The rotational constants have been determined for the vibrational levels concerned, and the coefficients α i have been determined with more convincing accuracy than previously. In some of the bands the Q branches have been resolved, so that the l -doubling coefficients q i could be derived, and details could be established about the doublet components in some II levels. The results emphasize the need of high resolution if the vibrational assignments are to be unambiguous, and if reliable values of the rotational constants are to be derived. A value of B e has been obtained, and the vibrational anharmonicity coefficients have been considered briefly. Estimates of the centrifugal stretching constants D i in different vibrational states have been made, and one anomalous case has been found.

High Resolution Infrared Spectra of the ν2 and 2ν1 Bands of 14N16O2

1975 ◽  
Vol 53 (19) ◽  
pp. 1902-1926 ◽  
Author(s):  
Aldée Cabana ◽  
Michel Laurin ◽  
Walter J. Lafferty ◽  
Robert L. Sams
Keyword(s):  
High Resolution ◽  
Infrared Spectra ◽  
Ground State ◽  
Equilibrium Structure ◽  
Coriolis Interaction ◽  
Rotational Constants ◽  
Average Structures

The infrared spectra of two B type bands, ν2 and 2ν1, of 14N16O2 have been recorded under high resolution. Ground state combination differences from these bands have been combined with combination differences obtained in previous studies and eight pure rotational microwave transitions to yield improved ground state rotational constants. Upper state constants and band centers for the ν2 and 2ν1 bands are also reported. The 2ν1 band contains internal intensity anomalies believed to arise from a weak Coriolis interaction with the much stronger ν1 + ν3 band. Equilibrium rotational constants have been calculated. The equilibrium structure of the molecule is: rc = 1.1945 ± 0.0005 Å and Θc = 133.85 ± 0.10°. For the sake of comparison, effective, substitution, and average structures are also reported.

Spectroscopic investigations of hydrogen bonding interactions in the gas phase. II. The determination of the geometry and potential constants of the hydrogen-bonded heterodimer CH 3 CN • • • HF from its microwave rotational spectrum

1980 ◽  
Vol 370 (1741) ◽  
pp. 239-255 ◽  
Keyword(s):  
Hydrogen Bonding ◽  
Gas Phase ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Hydrogen Bonding Interactions ◽  
Isotopic Species ◽  
Microwave Rotational Spectrum ◽  
Vibration Rotation ◽  
Hydrogen Bonded

The microwave rotational spectrum of the hydrogen-bonded heterodimer CH 3 CN • • • HF has been identified and shown to be characteristic of a symmetric top. A detailed analysis of several rotational transitions for a variety of isotopic species gives the spectroscopic constants summarized in the following table: Rotational constants/MHz, vibration-rotation constants/MHz and vibrational separations/cm -1 of CH 3 CN • • • HF

Vibration-rotation bands of acetylene and the molecular dimensions

1956 ◽  
Vol 238 (1212) ◽  
pp. 15-30 ◽  
Keyword(s):  
Molecular Vibrations ◽  
Rotational Constants ◽  
Bond Lengths ◽  
Vibrational Levels ◽  
Vibration Rotation ◽  
Molecular Dimensions

In view of recent inconsistencies in the relation between the bond lengths and rotational constants in the isotopic acetylenes, some vibration-rotation bands of acetylene have been re-measured, and the results have been analyzed together with earlier work on this molecule. The α values for each of the molecular vibrations have been re-determined, taking into account possible vibrational perturbations and also anomalous changes in the centrifugal stretching constant D of the different vibrational levels. The new values of α , 1 , α 2 , α 3 and ( α 4 + α 5 ) for acetylene are in line with the corresponding values for the deuterated derivatives, and using B o = 1·1766 lead to B e + 1·1817. If bond lengths r e (CH) = 1·058 5 , r e (CC) = l·204 7 Å are assumed, the results for all three isotopic molecules are mutually consistent. Values have also been obtained for the l -doubling coefficients, q 4 and q 5 .

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