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1.
By irradiating a mixture of CH3F highly diluted in Ar with a TEA CO2 laser, the v3 overtone emission rises with a rate much larger than the “up-the-ladder” V-V pumping rate indicating that the CH3F is excited up to the 3v3 level almost instantly. This occurs via multiple step excitation assisted by rotational transitions in collisions. 相似文献
2.
Previous works have reported vibration-vibration and vibration-translation transfer rates in CH3F and CH3FX mixtures. In this letter we report the study of the fast VV transfer rate populating the 3ν3, ν1 and ν4 states of CH3F. Gaseous CH3F was initially excited to the ν3 state by a TEA CO2 laser operating on the P(20 9.6 μ line and collisional pumping to the 3ν3, ν1 and ν4 states was measured by monitoring the rise time of the fluorescence at 300 cm−1. The rate constant was found to be 2.2 × 105 sec−1 torr−1. 相似文献
3.
Collisional energy transfer from CO2(ν3) to chloromethanes was studied in the temperature range 300–700 K using the laser induced fluoresce technique. Theoretical calculations using SSH and SB theories were carried out to identify the CO2(ν3) deactivation process. The experimental probabilities were found to decrease linearly with increasing number of substituted chlorine atoms. 相似文献
4.
Collisional energy transfer from CO2 to SO2 was studied subsequent to pumping of CO2 (ν3) by a Q-switched laser. The measurements were made in the temperature range 300–800 K and in the pressure range 1–30 Torr. The fluorescence from the ν3 level of CO2 was monitored with the help of a Ge:Au detector at 77 K with an estimated response time of ≈2 μs. The probability of the energy transfer was found to be increasing with increasing temperature. The probable kinetic models for the V---V relaxation pathways were discussed and the experimentally measured energy transfer rate is related to the cross-over transfer processes. Theoretical calculations using both a simple SSH-breathing sphere model and the Sharma-Brau theory were carried out to evaluate the probabilities of the involved cross-over energy transfer processes and the results were compared with the experimental rates. 相似文献
5.
epan S. Miljanic Bojan B. Radak Ljubica T. Petkovska 《Journal of Chemical Sciences》1991,103(3):405-408
Spectra of coincidence of CH3F IR absorption with CO2-laser emission at pressures of 2, 10 and 60 Torr were recorded by the use of a photoacoustic detection method in the whole
range of CO2-laser emission. The spectra show that CH3F absorbs many CO2-laser lines in the range 1084–1071 cm−1 with the strongest absorption at 1046.80cm−1, laser line P(20). Absorption is predominantly due to the fundamental of v3, which is well spread over the whole laser emission range. The intensities of all absorptions rise with increasing pressure,
but some absorptions change their relative intensity with respect to one another. In addition, the fine structure of the line
spectrum, characteristic of lower pressure samples, disappears as pressure is increased. 相似文献
6.
Infrared fluorescence has been observed from the ν1, ν6, 2ν9, ν8 and ν4 levels of CH2F2 following excitation by a 9.6 μ Q-switch CO2 laser. All the observed states exhibit a single exponential decay rate of approximately 44 msec?1 torr?1. The rare gas dependence of this rate has also been measured and found to be up to 20 times slower than the rate for the pure gas. Measurements of the risetimes of the observed fluorescence signals yielded an upper limit of 5 μsec at 1 torr for the ν1, ν6 and ν8 levels. The 2ν9 and ν4 risetimes were effectively instantaneous under the experimental conditions that prevailed. The relative magnitudes of the measured rate are discussed in terms of existing V-T/R theories and collisional energy transfer processes. 相似文献
7.
L. N. Krasnopyorov N. K. Serdyuk V. P. Strunin V. N. Panfilov 《Reaction Kinetics and Catalysis Letters》1977,7(3):321-326
The rate constants for Br(2P1/2) and Br(2P3/2) atoms in the reaction Br+CH3FHBr+CH2F in photobromination of CH3F have been determined. Their ratio is 10–(2.6±0.5) exp(10100±1000/RT) in the temperature range of 60–200 °C.
Br(2P1/2) Br(2P3/2) Br+CH3FHBr+CH2F CH3F. 60–200 °C 10–(2,6±0,5) exp (10100±1000/RT).相似文献
8.
In a molecular beam the effects of vibrational pumping of SF6 (ν3 = 948 cm?1) are studied, using a line-tunable cw CO2 laser. Intracavity spontaneous Raman scattering is used for analysis. For excitation in the collision regime (xE/D ≤ 1), a thermal redistribution of the ν3 excitation over all vibrational modes is found, together with an average absorption up to six photons per molecule. The infrared absorption profile shows a red-shift of 6 cm?1. For excitation in the relatively rare collision regime (xE/D ? 4), a structured non-thermal ν1 Raman spectrum is observed, especially in the case of seeded molecular beams (10% in He). The observed hot-band peaks can be explained in terms of single-photon absorptions and collision-induced near-resonant V-V energy transfer, leading to single, double and triple excitations of the ν3 mode. The value of Trot in the beam is found to influence sensitively the non-resonant energy-transfer rate [e.g. hν3(948 cm?1)+ΔErot → h(ν4 + ν6)(962 cm?1) relative to the near-resonant transfer rate (hν3 + hν3 → 2hν3 + 3.5 cm?1)]. 相似文献
9.
A CO2 TEA laser has been used to photolyze dilute samples of various alkyl halides in helium. The mechanism of the high intensity infrared photolysis of these molecules involves the decomposition of molecules into molecular or radical fragments. The reaction pathway is always dissociation into the lowest thermal dissociation channel(s) of the molecule photolyzed. Products from the initial process are also photo-dissociated by the laser pulse and their decomposition pathways are similarly governed. The molecules being photolyzed are not thermally equilibrated with the bath or with each other and the molecular-specific nature of the laser excitation is demonstrated. 相似文献
10.
A new experimental method is presented for measuring the multiple-photon dissociation rate of SF6. It appears that there is a reverse process which associates the photofragments into SF6. The measured dependence of the dissociation probability versus laser flux seems to agree qualitatively with theoretical models. 相似文献
11.
12.
Subsequent to exciting v3 by a CO2 laser pulse, fluorescence has been detected from 2v3 of CH3F trapped in rare gas matrices. 2v3 is activated by V-V energy transfer and deactivates at twice the rate of v3 relaxation. A kinetic model is presented to interpret these observations. 相似文献
13.
Multiple scattering Xα calculations with overlapping spheres were performed on CH3F and CH2F2 for all-valence region ionization potentials. Comparison with previous Xα calculations shows a substantial improvement. 相似文献
14.
Using the method of laser fluorescence, inelastic collisions with rare gas atoms of electronically excited 7Li2 molecules in the υ = 2 and 4 levels were studied. Vibrational transitions ranging from Δ = +2 to ?4 were observed. The simultaneous rotational transitions were completely resolved, and detailed rate constants kΔυ, ΔJ for specific collision- induced quantum jumps Δυ, ΔJ were determined. The effect of secondary rotational relaxation was eliminated by an extrapolation to zero pressure. By integration over ΔJ, rate constants kΔυ, were found. They are, within the error limits, independent of the collision partner and on the initial υ (2 or 4) and depend rather weakly on Δυ. These findings are compared with theoretical results from various methods, generally based on a collinear collision model. The apparent disagreement in all respects suggests strongly the importance of rotational degrees of freedom in the collision. Experimental evidence for this is the large amount of V — R transfer observed, which about equals the V — T transfer. The mean cross sections σ(Δυ) for specific vibrational transitions Δυ range between 6 and 15 A2, among the largest ever observed. 相似文献
15.
The state population of CF3Br is found to be entirely non-thermal under certain molecular beam conditions; the various vibrational modes show distributions which can be described using mode-temperatures differing by as much as a factor of 1.7. Considerable vibrational excitation (ν1, ν2 + ν3) was produced with a focused cw CO2 laser. A structured excitation spectrum was observed. 相似文献
16.
Inefficient vibrational energy exchange between the lowest vibrational mode and the higher lying vibrational modes of CH2Cl2, CD2Cl2, CH2ClBr and CH2Br2 was investigated by ultrasonic absorption experiments. Breathing sphere theory is used to interpret the data available for VV and VR, T transfer in methylene halides. 相似文献
17.
Osvaldo Goscinski Jiri Müller Enrique Poulain Hans Siegbahn 《Chemical physics letters》1978,55(3):407-412
Ab initio calculations within the Hartree-Fock formation have been carried out on potential energy surfaces of the ground and the F1s hole states of CH3F and CF4 in order to investigate linewidths of their ESCA spectra. The calculations show that potential energy surfaces of both hole states have dissociative character and can be approximated by straight lines in the region of interest. A simple formula for the ESCA fwhm linewidth is derived which yields results in good agreement with experiment. Theoretically derived relaxation and Koopmans' energies have been investigated as a function of geometry. 相似文献
18.
The liquid—solid equilibrium temperatures in the binary systems between n-octacosane and methyl or ethyl octadecanoate are determined in order to obtain the interchange parameters between CH3 or CH2 and COO groups by means of the statistics of group interaction. 相似文献
19.
Previous works have reported vibration—vibration and vibration—translation transfer rates in the methyl halides. Using the technique of laser induced infrared fluorescence we have studied energy transfer in the concluding member of this series, CH3I. Following excitation by resonant lines of a Q-switch CO2 laser, infrared fluorescence has been observed from the v2, v5 as well as the 2v5, v1, v4 vibrational energy levels of CH3I. All the observed states exhibit a single exponential decay rate of 23 ± 2 ms?1 torr?1. Measurements have also been made on deactivation of the various modes by rare gases. The risetime of the v2, v5 levels was found to be approximately 101 ± 20 ms?1 torr?1, while that of the 2v5, v1, v4 levels was approximately 225 ± 45 ms?1 torr?1. Fluorescence was not detected from the v3 level. These results are discussed in terms of SSH type theoretical calculations, and comparison is made with the results obtained for other members of the methyl halide series, namely CH3F, CH3Cl and CH3Br. 相似文献
20.
The photochlorination of methyl fluoride has been studied at low pressures. Excited (2P1/2) chlorine atoms have been found to participate in the reaction. The ratio of the excited and ground state rate constants has been estimated at room temperature.
. (2P1/2) . .相似文献