Absolute Raman intensities, force constants, and electro-optical parameters of CH₂Cl₂, CD₂Cl₂ and CHDCl₂

Abstract

The absolute Raman intensities and depolarization ratios of all the fundamental bands of CH2C12, CD~CI~ and CHDCI~ have been measured in the gas phase. These experimental data have been included in a refinement of the vibrational potential function of the dichloromethanes. A detailed description is made of the use of the bond polarizability approach. Explicit expressions for the derivatives of the molecular polarizability with respect to the symmetry coordinates are given in terms of the zeroth-and first-order electrooptical parameters of the theory. Good agreement is found between experimental and calculated intensities. The refined electro-optical parameters compare quite well with those obtained from methane, chloroform and carbon tetrachloride. The derivatives of the molecular polarizability with respect to the normal coordinates are also given.

Linear dependency in the refinement of force constants with the Jacobian method

“…15 The energy expression, which is a linear function of force constants in internal coordinates, is only nearly linear in Cartesian coordinates, and this accounts for the rapid convergence of the Jacobian method to yield a set of force constants which reproduce specified frequencies. For the sake of discussion, we will refer to the adjustment of frequencies by varying a set of force constants.…”

High-Resolution FTIR Spectra of CD235Cl2: Analysis of the ν3/ν7/ν9 Triad

“…In particular, quite unusually for a polyatomic molecule, no evidence of Fermi resonances has been found in CH 2 Cl 2 or CD 2 Cl 2 . An empirical general harmonic force field has been determined by Duncan et al (2) from the fundamental vibrations observed in infrared (1) and Raman spectra (3). They also derived several spectroscopic parameters, such as quartic centrifugal distortion constants, which can be tested against ground state constants obtained from microwave or far-infrared spectra, and Coriolis interaction constants, which might be valuable for the analysis of high-resolution infrared spectra.…”

“…They also derived several spectroscopic parameters, such as quartic centrifugal distortion constants, which can be tested against ground state constants obtained from microwave or far-infrared spectra, and Coriolis interaction constants, which might be valuable for the analysis of high-resolution infrared spectra. Several highresolution studies have been performed on CH 2 Cl 2 , including fundamental bands such as ν 3 and ν 9 which interact through a Supplementary data for this article may be found on the journal home page. 1 Correspondence address: Istituto di Fisica dell'Atmosfera, Via Fosso del Cavaliere, 100, 00133 Rome, Italy.…”

High Resolution IR Study of the Coriolis Coupling between ν3and ν9in Methylene Chloride

“…Raman spectra are reported in (7). Accurate ground state parameters have been determined using microwave (8)(9)(10) and far infrared data (9,10).…”