Vibrational temperature from rotational

Temperature from Rotational and Vibrational Raman Scattering Effects of Vibrational-Rotational Interactions and Other Corrections... 

The experimental results obtained by Fukutani et al. [8, 11] for NO and CO desorption from Pt(l 11) are summarized in Table 3. These results show clearly that the desorption is via a non-thermal process and induced by an electronic transition. The experimental results for NO desorption from Pt(00 1) at various photon energies observed by Fukutani et al. [5] are similar to those from Pt( 1 1 1) at A. = 352nm. Both rotational and vibrational temperatures from Pt(l 11) at X = 193 nm are higher than those at A. = 352 nm. Thus, the desorption from Pt(l 11) at X = 193 nm might proceed by a different path. 

S.4.2 Determining the vibrational temperature from the intensity distribution of vibrational-rotational Raman bands... 

Determination of the temperatures reached in a cavitating bubble has remained a difficult experimental problem. As a spectroscopic probe of the cavitation event, MBSL provides a solution. High-resolution MBSL spectra from silicone oil under Ar have been reported and analyzed.5 The observed emission comes from excited-state C2 and has been modeled with synthetic spectra as a function of rotational and vibrational temperatures. From comparison of synthetic to observed spectra, the effective cavitation temperature is 5,050 150K. 

In the same studies a determination of the vibrational temperature from the relative intensities of bands in the second positive system of N2 gave values in the range 2200-5000 K which did not change with increase in specific energy. Since the rotational temperature, probably close to the gas temperature, was almost 90% lower than the vibrational temperature, the plasma was non-isothermal under the experimental conditions which favored hydrazine formation. The non-equilibrium population of the highest vibrational levels of the nitrogen molecule has been adduced as indirect confirmation of the theory of energy catalysis (see Sect. 3). 

Spectroscopic investigations also showed that the introduction of the solid alkali did not lead to an anomalous population of rotational levels in NH but raised the vibrational temperature from = 3(XK) K to c= 4000 K. It was sugg ted that the recombination of ions, presumably N, on the catalyst surface leads to an increase in the number of nitrogen molecules at high levels of vibrational excitation. However, the location of NaOH catalyst at the cathode or anode does not influence significantly either the decomposition of ammonia or the synthesis of hydrazine (Fig. 25)... 

Figure A2.2.2. The rotational-vibrational specific heat, C, of the diatomic gases HD, HT and DT as a fiinction of temperature. From Statistical Mechanics by Raj Pathria. Reprinted by pennission of Butterwortii Heinemann.

Midey A J and Viggiano A A 1998 Rate constants for the reaction of Ar" with O2 and CO as a function of temperature from 300 to 1400 K derivation of rotational and vibrational energy effects J. Chem. Phys. at press... 

In order to see the effect of the rotational excitation of the parent H2O molecules on the OH vibrational state distribution, the experimental TOF spectrum of the H atom from photodissociation of a room temperature vapor H2O sample has also been measured with longer flight distance y 78 cm). By integrating each individual peak in the translational energy spectrum, the OH product vibrational distribution from H2O photodissociation at room temperature can be obtained. 

The overall OD vibrational distribution from the HOD photodissociation resembles that from the D2O photodissociation. Similarly, the OH vibrational distribution from the HOD photodissociation is similar to that from the H2O photodissociation. There are, however, notable differences for the OD products from HOD and D2O, similarly for the OH products from HOD and H2O. It is also clear that rotational temperatures are all quite cold for all OH (OD) products. From the above experimental results, the branching ratio of the H and D product channels from the HOD photodissociation can be estimated, since the mixed sample of H2O and D2O with 1 1 ratio can quickly reach equilibrium with the exact ratios of H2O, HOD and D2O known to be 1 2 1. Because the absorption spectrum of H2O at 157nm is a broadband transition, we can reasonably assume that the absorption cross-sections are the same for the three water isotopomer molecules. It is also quite obvious that the quantum yield of these molecules at 157 nm excitation should be unity since the A1B surface is purely repulsive and is not coupled to any other electronic surfaces. From the above measurement of the H-atom products from the mixed sample, the ratio of the H-atom products from HOD and H2O is determined to be 1.27. If we assume the quantum yield for H2O at 157 is unity, the quantum yield for the H production should be 0.64 (i.e. 1.27 divided by 2) since the HOD concentration is twice that of H2O in the mixed sample. Similarly, from the above measurement of the D-atom product from the mixed sample, we can actually determine the ratio of the D-atom products from HOD and D2O to be 0.52. Using the same assumption that the quantum yield of the D2O photodissociation at 157 nm is unity, the quantum yield of the D-atom production from the HOD photodissociation at 157 nm is determined to be 0.26. Therefore the total quantum yield for the H and D products from HOD is 0.64 + 0.26 = 0.90. This is a little bit smaller ( 10%) than 1 since the total quantum yield of the H and D productions from the HOD photodissociation should be unity because no other dissociation channel is present for the HOD photodissociation other than the H and D atom elimination processes. There are a couple of sources of error, however, in this estimation (a) the assumption that the absorption cross-sections of all three water isotopomers at 157 nm are exactly the same, and (b) the accuracy of the volume mixture in the... 

CF20—)m (—CF2CF20—) . This fluoropolymer has better low-temperature properties than Krytox, but is more expensive. Fomblin Z is made by photochemical polymerization of a mixture of oxygen and tetrafluoroethylene to prepare the random copolymer. The methylene oxide unit (—CF20—) imparts even more extraordinary low-temperature properties than those derived from vibration and free rotation of other perfluoroether linkages. 

Held together by electrostatic forces (or ion-ion interactions), as the temperature is raised towards 130°C, vibrational, translational and rotational motion increases. The oxygen ions in the nitrate cluster are indistinguishable from each other and this is said to make rotation of the nitrate ion easier. 

FIGURE 3.3 Schematic diagram of energy levels involved in HCI vibration-rotation transitions at room temperature (from Herzberg, 1950). 

Sonobe and Rosenfeld (48,49) have measured the 4.7 pm infrared emission of CO. The extent of the CO vibrational excitation can be estimated using a cold gas filter containing CO and a 4.7 pm filter. If CO is vibrationally excited there is a smaller amount of attenuation of 4.7 pm fluorescence by the cold gas filter. When ketene is photolyzed at 193 nm, they estimate from their data that the rotational and vibrational temperatures are about 6700 and 3700 K, respectively. A high rotational temperature suggests that the C-C-0 angle is bent in the excited state. The CO vibrational excitation becomes less for longer excitation wavelengths. 

Schematic energy level diagrams for the most widely used probe methods are shown in Fig. 1. In each case, light of a characteristic frequency is scattered, emitted, and/or absorbed by the molecule, so that a measurement of that frequency serves to identify the molecule probed. The intensity of scattered or emitted radiation can be related to the concentration of the molecule responsible. From measurements on different internal quantum states (vibrational and/or rotational) of the system, a population distribution can be obtained. If that degree of freedom is in thermal equilibrium within the flame, a temperature can be deduced if not, the population distribution itself is then of direct interest.

The temperature-dependent Raman spectra are depicted in Fig. 4-27a, b. Figure 4-27a shows the spectra of H2O-I (the water molecules in the inner coordination sphere) from 133-223 K. Figure 4-27b shows the spectra of H2O-II (the water molecules in the outer sphere). The spectra above 223 K are not shown because of the overlap with fluorescence that is observed with the 514.5 nm excitation. Plots of the variations of band frequency with temperature are illustrated in Fig. 4-28a, b for H2O-I and H2O-II. Two discontinuities are observed at 195 5K and 140 5K, indicative of three distinct phases occurring in the temperature range studied, as indicated in Fig. 4-28a. The higher-frequency OH stretch region, as shown in Fig. 4-28b does not show any discontinuities for H2O-I. A plot of full width at half maximum intensity (FWHM) vs. T for H2O-I shows a discontinuity at 140 K (Fig. 4-28c, d). Additional support for these phase transitions was found from the temperature dependences of the UO vibrational mode, lattice vibrations and the NO3 ion vibrations (translations and rotations). 

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