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1.
The emission spectrum of the dicyanoacetylene radical cation has been observed in the 580–720 nm wavelength region as a result of low energy electron impact excitation in a crossed-beam arrangement. The band system is attributed to the Ã2Σ+g → X?2Πu electronic transition by comparison with the photoelectron spectroscopic and calculated data on the states of dicyanoacetylene cation. The frequencies of the three Σ+g vibrational fundamentals in the ground cation state have been deduced from the emission spectrum. The lifetime of the lowest vibrational level of the Ã2Σ+g state of dicyanoacetylene cation was determined to be 13 ± 2 ns. Emission could not be detected from the corresponding states, Ã2Σ+, of fluorocyanoacetylene and cyanoacetylene cations, and these results are discussed.  相似文献   

2.
Several absorption lines in the B? 1Σ+u ← X 1Σ+g system at 83 nm have been observed with sub-Doppler resolution in H2 and HD. A detailed analysis of the lineshapes arising from the homogeneously predissociaied B 1Σ+u states shows that the linewidths are strongly affected by the Franck-Condon factors associated with coupling to the B' 1Σ+u continuum.  相似文献   

3.
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   

4.
Configuration interaction calculation are employed to study the X 2Σ+g, A 2Πu, B 2Σ+u, 4Σ+u and 4Δu states of the C?2 ion. The results are in good quantitative agreement with experimental findings for the Herzberg—Lagerquist (2Σ+u-2Σ+g) bands and predict a Te value for the 2Πu state of only 0.40 eV; corresponding transition moment results are obtained as a function of CC distance. The Cl electron affinity is 3.43 eV, in good agreement with the most recent experimental estimate for this quantity.  相似文献   

5.
Absolute emission cross sections have been determined for electron impact on CO, NO and N2. For the CO(A 1ΠX 1Σ+) and N2(a 1ΠX 1Σg) radiation our data is in good agreement with that of other groups. For CO+ (B2Σ+X2Σ+) the values of the emission cross sections are different from those measured previously. This discrepancy is explained in terms of an inadequate straylight correction in the former experiments. For the NO(A2Σ+X2Π) emission no previous σem values are known to the authors. Furthermore the electronic transition moments of the NO(A2Σ+X2Π) and CO+(B2ΣX2Σ+) systems have been measured and are found to be independent of the internuclear distance.  相似文献   

6.
Time-resolved measurement of He (2 3S) concentration by its optical absorption after electron pulse irradiation of HeN2 mixtures confirms that the optical emission of N+2(B 2Σ+u → X 2Σ+g) is based on the energy transfer (Penning ionization) from He (2 3S) to N2. The addition of other atoms and molecules to HeN2 mixtures changes the decay rate of the optical emission N+2(B 2Σ+u → X 2Σ+g), which is a detector of He (2 3S), and gives the rate constant of He (2 3S) de-excitation by various atoms and molecules. Our results are discussed from the viewpoint of a gas-kinetic collision model.  相似文献   

7.
Within Lichten's method, shielded diatomic orbitals (SDO's) are proposed as a basis for building-up diabatic molecular states in the single configurati approximation. The determination of SDO's i.e. eigenfunctions in prolate spheroidal coordinates of the two-center problem with a parametric shielding potential is extended to mono-excited states of many-electron diatomic systems, the shielding potential being obtained from simple electrostatic considerations. Four diabatic molecular states of H2 are investigated i.e. 1Σg+ (2pσ2, 1Σg+ (1s,σ 2sσ), 1Σu+(1sσ,4Pσ), 1Σu+ (1sσ, 4fσ) using a minimal basis of SDO'S. The dynamical evolution of the nuclei for the two sets 1Σg and 1Σu+ of two interacting states is described in both the diabatic and the corresponding adiabatic representation.  相似文献   

8.
9.
Cross sections for collision induced dissociation of 0.65 to 3.2 keV I+2(2Πg, υ) ions in I+2(2Πg, υ) + N2(X 1Σ+g, υ = 0) interactions have been determined. Reaction cross sections for I+2(2Π32,g, υ) ions in low vibrational levels vary smoothly from 6 to 10 A2 with increasing kinetic energy. Dissociation cross sections for I+2(2Π12,g, υ) ions are larger than those involving ground state ions. Processes involving highly excited metastable states of I+2 are not observed in this investigation.  相似文献   

10.
Time-resolved excitation spectra of xenon vapor in the 150 nm region are analysed in terms of four main fluorescence lifetimes corresponding to decays of four stable excited electronic states of the Xe dimer. The two shortest decay times, ≈ 2 ns and ≈ 60 ns, are assigned to the direct radiative relaxation of the two lowest excited ungerade states, (1Σ+u)0+u and (3Σ+u))1 u respectively. The two longest decay times, ≈ 150 ns and ≈ 500 ns, must correspond to the overall depopulation rates of the two lowest excited gerade states, (3Σ+g)1g and (1Σ+g)0+g, decaying into the gerade ground state by cascading down through the intermediate ungerade states.  相似文献   

11.
The long sought‐after, intrinsically short‐lived molecule ethylenedione (OCCO) was observed and investigated by anion photoelectron spectroscopy. The adiabatic electron affinity of its quasi‐bound 3Σg? state is 1.936(8) eV. The vibrational progression with a 417(15) cm?1 frequency observed within the triplet band corresponds to a trans‐bending mode. Several dissociative singlet states are also observed, corresponding to two components of the 1Δg state and the 1Σg+ state. The experimental results are in agreement with theoretical predictions and constitute the first spectroscopic observation and characterization of this elusive compound.  相似文献   

12.
The absorption of photons by Li2 from the X 1Σ+g state to the A 1Σ+u and B 1Πu states is considered and the mechanisms that lead to dissociation are studied quantitatively. Calculations are reported on the direct predissociation of the b 3Πu state. The significance of accidental predissociation of the A 1Σ+u state is discussed and a quantal theory of the process is presented.  相似文献   

13.
The 300 K reactions of O2 with C2(X 1Σ+g), C2(a 3 Πu), C3(X? 1Σ+g) and CN(X 2Σ+), which are generated via IR multiple photon dissociation (MPD), are reported. From the spectrally resolved chemiluminescence produced via the IR MPD of C2H3CN in the presence of O2, CO molecules in the a 3Σ+, d 3Δi, and e 3Σ? states were identified, as well as CH(A 2Δ) and CN(B 2Σ+) radicals. Observation of time resolved chemiluminescence reveals that the electronically excited CO molecules are formed via the single-step reactions C2(X 1Σ+g, a 3Πu) + O2 → CO(X 1Σ+ + CO(T), where T denotes are electronically excited triplet state of CO. The rate coefficients for the removal of C2(X 1Σ+g) and C2(a 3Πu) by O2 were determined both from laser induced fluorescence of C2(X 1Σ+g) and C2(a 3Πu), and from the time resolved chemiluminescence from excited CO molecules, and are both (3.0 ± 0.2)10?12 cm3 molec?1 s?1. The rate coefficient of the reaction of C3 with O2, which was determined using the IR MPD of allene as the source of C3 molecules, is <2 × 10?14 cm3 molec?1 s?1. In addition, we find that rate coefficients for C3 reactions with N2, NO, CH4, and C3H6 are all < × 10?14 cm3 molec?1 s?1. Excited CH molecules are produced in a reaction which proceeds with a rate coefficient of (2.6 ± 0.2)10?11 cm3 molec?1 s?1. Possible reactions which may be the source of these radicals are discussed. The reaction of CN with O2 produces NCO in vibrationally excited states. Radiative lifetime of the ā 2Σ state of NCo and the ā 1Πu(000) state of C3 are reported.  相似文献   

14.
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   

15.
Lifetimes of C-2 in rotational levels of the B?2Σ+u:ν′ = 0, ν′ = 1 states have been measured. C-2 was produced from bromoacetylene and rare-gas metastables and the B?2Σ+u—X?2Σ+g transition was laser excited. The lifetimes are constant within a vibrational level, 77 = 8 ns for ν′= 0 and 73 = 7 ns for ν′ = 1. The oscillator strength fνo = 0.044 ± 0.004.  相似文献   

16.
The long sought‐after, intrinsically short‐lived molecule ethylenedione (OCCO) was observed and investigated by anion photoelectron spectroscopy. The adiabatic electron affinity of its quasi‐bound 3Σg state is 1.936(8) eV. The vibrational progression with a 417(15) cm−1 frequency observed within the triplet band corresponds to a trans‐bending mode. Several dissociative singlet states are also observed, corresponding to two components of the 1Δg state and the 1Σg+ state. The experimental results are in agreement with theoretical predictions and constitute the first spectroscopic observation and characterization of this elusive compound.  相似文献   

17.
The Equations of Motion method has been applied in the calculation of potential energy curves for the X2Σ+g, A2Πu and B2Σ+u states of N+2. Results are also reported for a new dissociative 2Σ+g state. The theoretical curves are directly compared with the experimental ones as well as in terms of spectroscopic constants. The applicability of the Equations of Motion method to this type of problem is critically examined and discussed with regard to the choice of basis set, numerical effort and agreement with experiment.  相似文献   

18.
The kinetic energy distribution of the O+ ions formed by dissociative ionization of O2 has been carefully examined in the range of 0.0 to 1.3 eV. In the peak at 600 meV fine structure is observed and interpreted by predissociation. The high energy side of the peak has been ascribed to the predissociation of the 2Δg, B2Σ?g and the C4Σ?u states of O+2. The low energy side of the peak is presumably due to the predissociation of the b4Σ?g state or the 2Φu state of O+2 or to autoionizing predissociation.  相似文献   

19.
Structure has been observed in the ≈ 0.8 eV kinetic energy O+ ion peak produced by electron impact dissociative ionization of O2. The spacing between the features observed is approximately 0.08 eV which is consistent with their originating through predissociation of the B 2Σg? state of O+.  相似文献   

20.
A number of dissociation channels in N20 have been observed by time-of-flight spectroscopy following electron impact excitation. The metastable atoms and molecules produced were directly detected. Excited N2 molecules were produced in the A3Σu+, B3Πg and B′3Σu? states in conjunction with ground state oxygen atoms. A number of additional dissociation channels were monitored by observing the production of oxygen and nitrogen atoms in Rydberg states. The results indicate the existence of potential minima in some of the repulsive surfaces involved.  相似文献   

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