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1.
The vibrational analysis of the CN(B2Σ+ → X2Σ+) emission sensitized by Hg(63P0) metastables has shown that the energy transfer process, Hg(63P0) + CN(X2Σ+) → Hg(61S0) + CN(B2Σ+), populates the CN(B2Σ+) state in a non-Franck-Condon fashion. The relative vibrational populations for the ν = 0 to 4 states are 1.00, 0.56 ± 0.06, 0.26 ± 0.03, 0.11 ± 0.03 and 0.04 ± 0.01, respectively. Long-range attractive interaction between the Hg(63P0) atom and the CN(X2Σ+) radical is evidenced by the observed high rotational excitation of the CN(B2Σ+) radical following the energy transfer process.  相似文献   

2.
A pulsed ICR cell fitted with synchronous photon counting equipment is used to investigate the emission produced between 185 and 500 nm by near-thermal charge exchange between He+ and C2H2 (C2D2). The emission bands observed are A 2Δ → X2π and (weakly) B2Σ? → X2π in CH(CD) and A 1π → X1Σ in CH+(CD+). Wavelength measurements on the bandheads of the (0,0) and (0,1) bands of CD+ A → X are used to evaluate vibrational constants of CH+(CD+) X1Σ+. The results are (in cm?1): ωe = 2869 ± 27 (2106 ± 20); ωeχe = 65 ± 13 (35 ± 7). These constants are used to calculate Morse-potential Franck—Condon factors and vibrational branching ratios for CH+ and CD+ A → X emission. The spectral distributions and the (relatively low) absolute emission rates produced by He+/C2H2(C2D2) charge exchange are briefly discussed in the light of presently available information on the charge transfer reaction and on the excited states of C2H2?+  相似文献   

3.
A comparative spectroscopic study in the visible and ultraviolet ranges was conducted on the flowing afterglows resulting from the reactions of He(2 3S) and Ne(3P0,2) metastables with CS2. Penning ionization was found to be the predominant energy transfer process. However, electron—ion recombination within the afterglows constitutes a major secondary process and gives rise to the most intense emitting system, CS(A 1 Π → X 1Σ+). Both afterglows were found to produce the CS+2(B2Σ+u-X2Πg), CS+2(A2Πu-X2Πg) and CS(a 3Π-X 1Σ+) emission systems as well as some atomic sulfur emission lines. Some intensity differences were observed and are interpreted in terms of energetics and the formation mechanisms of the emitting species. A moderately strong CS+(A 2Πi-X 2Σ+) emission system was also observed in the ehlium afterglow. In addition, a weak, sharp group of bands in the 390–420 nm range in the helium afterglow has been determined to be due to the presence of a small amount of He+ ions. This group of bands consists of two overlapping emission systems and are identified as CS(B 1Σ+ → A 1Π) and CS+(B 2Σ+ → A 2Πi).  相似文献   

4.
The fluorescence transitions corresponding to the second positive system of N2 (C3Πu → B3Πg) for Δv = 0, 1 and the first negative system of N+2(B2Σ+u → X2Σ+g) for Δv = 0, 1, 2 have been observed following laser-induced mul excitation of N2.  相似文献   

5.
The energy transfer reation of He(23S) + CS was studied spectroscopically in a flowing afterglow apparatus. The CS+(B2Σ+ → A 2Πi) transition is identified via three members of the Δν = 0 sequence (406–415 nm). The spin-orbit splitting of the (0, 0) band of CS+(A 2Πi) is 301 ± 5 cm?1. A weak emitting system (280–340 nm) is tentatively identified as CS+(B2Σ+→ X2Σ+).  相似文献   

6.
Ab initio calculations are performed to obtain potential energy curves for the X1Σg+ state of Li2 and Na2 and the X2Σg+ and A2Σg+ states of their anions. The A2Σg+ M2? curves are found to intersect the X1Σg+M2 curves at low energies and are expected to play a major role in the e? + M2 → M? + M process.  相似文献   

7.
Spectra emitted from 0.1% CO-N2 solids excited with high energy electrons at 4 K show evidence for resonant transfer of vibrational energy from highly excited vibrational levels of N2 to CO in the process N2(X1Σg+, ν) + CO(ν = 0) → N2(X1Σg+, ν - 1) + CO(ν = 1) + phonons. Energy transfer from levels with ν ? 9 has been observed.  相似文献   

8.
An ICR spectrometer fitted with synchronous photon counting equipment is used to study the emission produced by near-thermal (? 0.1 eV) collisions between He+ and H2O (D2). Within the investigated wavelength region, 185 to 500 nm, the only significant emission features are the A3Π (υ' ? 3) → X3Σ? bands in OH+ and OD+, and the A2Σ+ → X2Π(0.0) band in OH and, possibly, in OD. The corresponding excitation rate constants represent only ? 2% of the total He+/H2O (D2O) charge transfer. The resonant electron-jump model for thermal-energy charge exchange is discussed in the light of recent information on the He+/H2O reaction and on the excited states of H2O+ and their excitation by electron and photon impact on H2O (D2O).  相似文献   

9.
Photoelectron energy and angular distributions are measured for the 2+1 multiphoton ionization process H2 X1Σg+ (ν = 0,J) + 2hv → E,F1Σg+E,JE = J) + hν → H2+X2Σg++) + e?, for νE = 0, 1, or 2 and for JE = 0 or 1 of the inner well of the double-minimum E,F state. Although a strong preference is found for ν+ = νE, the detailed H2+ vibrational distribution does not exhibit Franck-Condon behavior, and the photoelectron angular distributions vary markedly with both the JE value of the intermediate state and the ν+ value of the ion.  相似文献   

10.
NH(A3Π → X3Σ?) and OH(A2Σ+ → X2Π) chemiluminescences from the reaction of CH(X2Π) with NO and O2, respectively, have been observed at room temperature. From the decay of such emissions we have measured the rate constants for these two reactions: kNO = (2.5 ± 0.5) × 10?10 and kO2 = (8 ± 3) × 10?11 cm3 molecule ?1 s?1, which are in agreement with previously reported rates determined by direct CH(X) detection using, laser-induced fluorescence. This indicates that a four-centered mechanism generating these excited species is operative in both reactions. The CH generation from 266 nm photolysis of CHBr3 has also been investigated via analysis of CH* emissions.  相似文献   

11.
Chemiluminescence from the b 0+ → X1 0+ band system of AsI and of the b 0+ → X1 0+, X2 1 systems of SbI in the near-infrared spectral region has been observed in a discharge flow system. Analysis of the spectra led to the spectroscopic constants (in cm?1) of AsI: ωe(X1, X2) = 257 ± 2, ωexe(X1, X2) = 0.82 ± 0.2, Te(b 0+) = 11738 ± 5, ωe(b 0+) = 271 ± 2, ωexe(b 0+) = 0.66 ± 0.2, and of SbI: Te(X2 1) = 965 ± 10, ωe(X1, X2) = 206 ± 6, Te(b 0+) = 12328 ± 10, ωe(b 0+) = 211 ± 6. The intensity ratio of the two sub-systems b 0+ → X2 1 and b 0+→ X1 0+ was found to be ≈0.013 in the case of SbI and ? 0.01 for AsI.  相似文献   

12.
Integral cross sections for pure rotational and vibrational-rotational excitation of H2(X1Σ+g) by Li+(1S) impact are computed by close-coupling methods at 0.2, 0.6, and 1.2 eV in the c.m. system using vibrational functions that are numerical solutions of the one-dimensional radial Schrödinger equation for harmonic, Morse, and adiabatically corrected Kolos-Wolniewicz (KW) potential functions. Comparison of results employing KW and Morse functions shows excellent agreement for all transitions studied. Findings using harmonic oscillator functions, however, differ noticeably from KW and Morse values for vibrational (0 → 1) and very large rotational (Δj = 10) transitions, but are satisfactory for lower order (0 → 2, 4, 6, 8) rotational transitions.  相似文献   

13.
The electronic energy transfer process Hg(6 3P0) + OH(X2Πi, υ = 0,K) → Hg(6 1S0) + OH(A 2Σ+, υ,K) has been studied by the sensitized fluorescence method. A rather broad spectrum of rotational population, Nυ′K, was obtained under conditions of minimum relaxation, which illustrates the non-resonant and non-optical nature of this energy transfer process. The fractions of the exoergicity, above electronic excitation of OH(A 2Σ+, υ = 0, K = 0), going into vibrational, rotational and translational excitation are 0.11, 0.31, and 0.58, respectively. A statistical mode of energy partitioning, such as would result from long-lived complex formation, seems to account well for these observations.  相似文献   

14.
Strongly enhanced N2 first positive emission N2(B 3Πg → A 3Σ+u) has been observed on addition of N atoms into a flowing mixture of Cl and HN3. The dependence of the emission intensity on N atom concentration gave a rate constant for the reaction N + N3 → N2(B 3Πg) + N2(X 1Σ+g) of i(1.6 ± 1.1) × 10?11 cm3 molecule?1 s?1. That for the reaction Cl + HN3 → HCl + N3 is (8.9 ± 1.0) × 10?13 cm3 molecule?1 s?1 from the decay of the emission. Comparison of the emission intensity in ClHN3 with that in ClHN3N gave the rate constant of the reaction N3 + N3 → N2(B 3Πg) + 2N2(X 1Σ+g) as 1.4 × 10?12 cm3 molecule?1 s?1 on the assumption that N + N3 yields only N2(B 3Πg) + N2(X 1Σ+g).  相似文献   

15.
Time-resolved investigations of the atomic resonance fluorescence Sr(53P1 → 51S0) and the molecular chemiluminescence from SrCl(A2Π1/2,3/2, B2Σ+ → X2Σ+) are reported following the reaction of the electronically excited strontium atom, Sr(5s5p(3PJ)), 1.807 eV above its 5s2(1S0) electronic ground state, with CH2Cl2. The optically metastable strontium atom was generated by pulsed dye-laser excitation of ground state strontium vapor to the Sr(53P1) state at λ = 689.3 nm (Sr(53P1 ← 51S0)) at elevated temperature (850 K) in the presence of excess helium buffer gas in which rapid Boltzmann equilibration within the 53PJ manifold takes place. Sr(53PJ) was then monitored by time-resolved atomic fluorescence from Sr(53P1) at the resonance wavelength together with chemiluminescence from electronically excited SrCl resulting from reaction of the excited atom with CH2Cl2. The molecular systems recorded in the time-domain were SrCl(A2Π1/2 → X2Σ+) (Δν = 0, λ = 674 nm), SrCl(A2Π3/2 → X2Σ+) (Δν = 0, λ = 660 nm), and SrCl(B2Σ+ → X2Σ+) (Δν = 0, λ = 636 nm). Both the A2Π (179.0 kJ mol?1) and (B2Σ+(188.0) kJ mol?1) states of SrCl are energetically accessible on collision between Sr(3P) and CH2Cl2. Exponential decay profiles for both the atomic and molecular (A,B – X) chemiluminescence emission are observed and the first-order decay coefficients characterized in each case. These are found to be equal under identical conditions and hence SrCl(A2Π, B2Σ+) are shown to arise from direct Cl-atom abstractions on reaction with this halogenated species. The combination of integrated molecular and atomic intensity measurements, coupled with optical sensitivity calibration, yields estimations of the branching ratios into the A1/2,3/2, B, and X states arising from Sr(53 PJ) + CH2Cl2 which are found to be as follows: A1/2, 3.0 × 10?3; A3/2, 1.7 × 10?3; B, 4.4 × 10?4 yielding ΣSrCl(A1/2 + A3/2 + B) = 5.1 × 10?3. As only the X, A and B states of SrCl are accessible on reaction, this indicates an upper limit for the branching ratio into the ground state of 0.995. The present results are compared with previous time-resolved measurements on SrF, Cl, Br(A2Π,B2Σ+ ? X2Σ+) that we have reported on various halogenated species and with analogous chemiluminescence studies on Sr(3P) with other halides obtained from molecular beam measurements. The results are further compared with those from a series of previous analogous investigations in the time-domain we have presented of molecular emissions from CaF, Cl, Br, I (A,B – X) arising from the collisions of Ca(43PJ) with appropriate halides and with branching ratio data for Ca(43PJ) obtained in beam measurements. © 1995 John Wiley & Sons, Inc.  相似文献   

16.
Chemiluminescence studies of the reactions of microwave-discharged oxygen with SbBr3 have led to the observation of some band sequences in the near infrared region which are attributed to b0+ → X10+ and b0+ → X21 transitions of SbBr. Analysis of the spectra yielded Te values for the X21 and b0+ states of 874 ± 10 and 12756 ± 10 cm?1, respectively, and vibrational frequencies in the X10+, X21 and b0+ states of ω′'e(X1, X2) = 257 ± 10 and ω′e(b) = 270 ± 10cm?1.  相似文献   

17.
Silicon atoms react under single collision conditions with N2O to yield chemiluminescent emission corresponding to the SiO a3Σ+?X1Σ+ and b3Π?X1Σ+ intercombination systems and the A1Π?X1Σ+ band system. A most striking feature of the SiN2O reaction is the energy balance associated with the formation of SiO product molecules in the A1Π and b3Π states. A significant energy discrepancy ( = 10000 cm? = 1.24 eV) is found between the available energy to populate the highest energetically accessible excited-state quantum levels and the highest quantum level from which emission is observed. It is suggested that this discrepancy may result from the formation of vibrationally excited N2 in a concerted fast SiN2O reactive encounter. Emission from the SiO a3Σ+ (A1Π) and b3Π(A1Π, E1Σ0+) triplet-state manifold results primarily from intensity borrowing involving the indicated singlet states. Perturbation calculations indicate the magnitude of the mixing between the b3Π, A1Π and E1Σ0+ states ranges between 0.5 and 2%. On the basis of these calculations, the branching ratio (excited triplet)/(excited singlet) is found to be well in excess of 500. An approximate vibrational population distribution is deduced for those molecules formed in the b3Π state. The present studies are correlated with those of previous workers in order to provide an explanation for diverse relaxation effects as well as observed changes in the ratio of a3Σ+ to b3Π emission as a function of pressure and experimental environment. Some of these effects are attributable to a strong coupling between the a3Σ+ and b3Π state. Based on the current results, there appears to be little correlation between either (1) the branching ratio for excited state formation or (2) the total absolute cross section for excited-state formation and (3) the measured quantum yield for the SiN2O reaction. Implications for chemical laser development are considered.  相似文献   

18.
The reactions of CS(X 1Σ+), CS2(X 1Σ+g) and OCS(X 1Σ+) with O(3P) were studied at 298 K by means of a CO laser resonance absorption technique. The CO(ν) population distribution produced from the reaction O(3P) + CS(X 1Σ+) studied in a quartz flash photolysis tube (λ>/ 200 nm) is similar to distributions observed previously for ν> 7. For ν < 7 an energetically colder vibrational population was observed which is attributed to the reaction of O(3P) atoms with undissociated CS2(X 1Σ+g). Subsequent experiments carried out in a Pyrex flash photolysis tube (λ>/ 300 nm) in which the O(3P) + CS2(X 1Σ+g) reaction is the only one which can occur confirmed that the colder population observed is attributable to this process. The branching ratio for the reaction channel O(3P) + CS2(X 1Σ+g) → CO(X 1Σ+) + S2(3Σ?g) has been measured. We find that 1.4 ± 0.2% of the O + CS2 reaction proceeds through this channel, and that the rate constant for this reaction channel is, k = 3.5 (±0.5) × 1010 cm3/mole s. Isotope labeled experiments using 18O atoms show that the O(3P) + OCS(X 1Σ+) reaction takes place by a direct stripping mechanism, wherein CO(ν) is produced exclusively from the parent OCS molecule. The CO(ν) formed in this reaction carries about 9% of the total available energy.  相似文献   

19.
The relative oscillator strength of the A 2Hi → B 2Σ+ transition has been measured by comparing the laser-induced fluorescence signal from excitation of a known distribution of CN A 2Hi and CN B 2Σ+ produced by the photodissociation of cyanogen at 158 nm. The oscillator strength of the A 2Hi → B 2Σ+ transition is 0.011 ± 0.006 times that of the X 2Σ+ → B 2Σ+ system. This leads to a value of (4.0 ± 2.2) × 10?4 for the band oscillator strength.  相似文献   

20.
A measurement of the electronic transition moment variation for the N2(a'1Σ?uX1Σ+g) band system has allowed a reassessment of the radiative lifetime of N2(a′). Relaxation to N2(a′,υ=0) is established as the major channel for quenching of N2(a1Πg, υ = 0) molecules by Ar.  相似文献   

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