Mechanistic interpretations of vibrational dephasing processes in 1,1,1‐trichloroethane by spontaneous Raman spectroscopy

Dehart

1980

The Raman signal from the v1 mode of trichlorosilane has been examined by dilution in several solvents. Temperature studies were also conducted and include data from the disordered solid phase of the neat sample. The results of these studies show that (a) the v1 fundamental is involved in a dephasing process controlled by the intramolecular potential function; (b) the neat liquid has a longer dephasing time than in any of the solvents, indicating memory retention as an intermolecular process. Additionally, environmental effects (broadening) are pronounced and appear to be related to the dipole moment of the solvent. The theoretical model proposed by Rothschild' is used to strengthen the interpretive case offered for the dephasing mechanistic process of the fundamental.

Section: A Theoretical Model Of Tcsmentioning

confidence: 82%

Vibrational dephasing of the SiH stretching mode in liquid trichlorosilane

Dehart

1980

Vibrational dephasing in polar molecular liquids: An application to a fundamental and its overtone in phenyl acetylene

1980

Based upon the results reported here for phenyl acetylene and the results of other investigators' studies, a working model of phase relaxation in polar molecular liquids is proposed. The model rests upon the established concept of a phase annihilation operator' and a postulated phase conduction band structure for polar molecular liquids. Three cases are discussed; briefly, they are (I) no effect upon the signal of interest by dilution, (11) narrowing of the signal of interest by dilution, and (111) broadening of the signal of interest by dilution. The latest effect has not been elucidated previously in the literature. Actual examples of each of these cases are discussed. Phenyl acetylene's vcc and 2vcc modes are shown to display Case I1 behavior. These two modes are found in the Raman spectrum at 2113 Em-' (vcc) and 4205 Em-' (2vcc). They have been examined by varying the concentration of this molecule in two dipolar solvents, a quadrupolar solvent and an octopolar solvent. In addition, temperature studies on the neat sample were carried out at 10-30 K intervals for vcc and at 275 K and 90 K for 2vcc. From the results of our investigation, a relaxation mechanism consistent with a quadrupolequadrupole dephasing type mechanism is postulated for both vcc and 2vcc.

Reorientational dynamics of liquid CH₃CCl₃ by Raman spectroscopy

Tsai

1981

Spontaneous Raman spectra of the 2940 em-' signal of liquid l,l,l-trichloroethane (TCE) were studied in order to obtain information concerning the molecular reorientation process. The reorientational correlation time was measured as a function of temperature between 255 and 298K giving an activation energy of 2.6 cal mol-' for the tumbling motion of neat liquid TCE. Experimental results were compared with those from extended &diffusion model, microviscosity theory and previous work. It was found that the TCE molecules underwent small-step rotational diffusion. The large variation of the reorientational correlation functions and rotational correlation times of TCE in dilute solutions of CCI,, CDCI3 and CD3CN suggested that the dipole moment contribution is an important factor in molecular reorientation in solutions as suggested by Larkin.