Raman frequency and intensity measurements have been performed on liquid water as H,O, D,O and HZ1'0 to study the effects of isotope substitution. Intensity data were collected digitally, normalized to account for the temperature and frequency factors and presented in isotropic and anisotropic forms. The frequency and intensity changes are consistent with the predictions of simple reduced mass calculations. In particular, there was no evidence to support the reported breakdown of the Born-Oppenheimer approximation as has been reported for H, "0. The isotope invariant sum rule was checked for H2I60, H,"O and D,O by relative intensity studies for the OH stretching region against an internal sulfate reference peak. Identical values for the isotope invariant sum were obtained for H,160 and H2"0 but the value for DzO was about 30% larger. The difference appears to have its origin in the more highly structured nature of D,O due to smaller anharmonic effects. Accurate frequency shifts among H, l6O, H,"O and D,O are also presented. Surprisingly, the greatest frequency shift which accompanied "0 substitution was in the low-frequency hydrogen-bonded region where the band at 192 cm-' for H,O shifted by 15 cm-I to 177 cm-' for H,"O. This result confirms previous observations and establishes the origin of this band as a hydrogen-bonded symmetric stretching mode which involves primarily oxygen displacement. Further support for this assignment comes from the observation that the band at 192 cm-' is slightly polarized. The effects of intermolecular coupling contribute to the band structure of the internal modes. Frequency differences in the OH stretching region of H,O and Hzl'O suggest that only about 50% of the anisotropic intensity is due to the Raman activity of the v3 antisymmetric stretching mode while the remainder is due to the symmetric stretching modes of intermolecularly coupled water molecules. A point-by-point comparison of the OH stretching region for the isotropic scattered intensity of H,O and H,"0 revealed that the complete region from 2800 to 3800 cm-I was shifted equally by 7 cm-', a fact that suggests that the peak maximum at about 3250 cm-a is just part of the v1 symmetric stretching mode and is not primarily due to 2v,. The effect of intermolecular coupling in the v, region of liquid water was confirmed by the difference in the frequency for the isotropic and anisotropic components for each of the isotopic forms of water. For H,"0 the peak maximum in the isotropic spectrum was at 1619 cm-' whereas the peak maximum in the anisotropic spectrum was at 1637 cm-with the result that in the measured I,, spectrum the peak maximum was at 1629 cm-'.

Laser-induced fluorescence has been used to examine the temporal behavior of ground-state CF2 and CF radicals in a CF4 plasma etching reactor. We also report the measured spatial dependencies of the radical concentrations, and develop a rigorous model for their interpretation. The results indicate that for CF2 and CF, wall removal processes are dominant at low pressures of the order of 50 mTorr, and that CF is not produced by electron impact dissociation of CF2.

Time resolved fluorescence from the first excited (2A1) state of NH2 has been observed following excitation of the radical in its ground state by means of a pulsed tunable dye laser. Specific rotational levels within a number of vibronic states were populated, decay rates measured as a function of total pressure for a variety of added gases, and zero pressure lifetimes and collisional de-excitation rates evaluated. Measured zero pressure lifetimes are good approximations to the vibrational state radiative lifetimes, typically 10 μsec for the (0, 9, 0) state. Collisional de-excitation rate constants were measured as 1.0×10−9 cm3 molecule−1⋅sec−1 for NH3, independent of vibronic state, and for the Σ (0, 9, 0) level were found for other gases in the ratio NH3:CO:H2:N2:CH4:Ar:He=1.0:0.47:0.46:0. 40:0.30:0.152:0.145. Using excitation by a tunable cw dye laser, steady state spectra of NH2 have been obtained and collisional energy transfer observed within the (2A1) excited electronic state of NH2. Transfer was observed both within the initially populated vibronic state and to other such states within the same overall vibrational level. The symmetric or antisymmetric character of the rotational level remained unchanged in collision, i.e., only a↔a and s↔s transfer occurred.

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A study has been made of the infrared chemiluminescence emitted from vibrationally excited CO o+cs2+so+cs, 0 + cs+co+ s, formed in the reaction sequence : when 0 atoms and CS2, highly diluted in Ar, were mixed in a flow system. Relative vibrational populations were determined from the first overtone band spectra. Some of the relative rates at which CO is produced in different levels (R,) were derived using a steady state analysis, in which the total rate of production of molecules in each vibrational level was equated to their total rate of removal. This gave : R74.1 ; R8 = 0.21 ; R9 = 0.49 ; Rlo = 0.61 ; Rll = 0.73 ; R12 = 0.91 ; R13 = 1.0; R14 = 0.92; R15 = 0.3. The results are discussed briefly in terms of the molecular dynamics of the reactive encounters and the nature of the potential energy hypersurface for reaction.

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