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1.
A mixture of NF3 and Ar is passed through an rf discharge in a flow-system to produce, among other species, F and NF2. When H2, D2, or CH4 are added downstream, reactions with F atoms produce vibrationally excited HF or DF together with H, D, or CH3. The latter free radicals can react with NF2, probably by an elimination reaction to produce electronically excited NF: NF2(2B1) + H(D, CH3) → HF*(DF* + NF(a1Δ). A vibrational-to-electronic energy transfer process between the products of this reaction then produces the next higher state of NF: HF(ν 2) + NF(a1Δ) → HF(ν−2) + NF(b1Σ+). A similar transfer process has also been found between the electronically excited a1Δ states of O2 and NF: O2(a1Δ) + NF(a1Δ) → O2(X3Σ) + NF(b1Σ+). The H or D atoms but not the CH3 radicals are then found to react with either NF(a1Δ) or NF(X3Σ) to produce electronically excited N(2D) atoms, which in turn react with the NF(a1Δ) molecules to produce N2(B3Πg). The observed nitrogen first positive radiation has been demonstrated to be produced entirely by this reaction mechanism rather than by the N(4S) recombination that accounts for the Rayleigh afterglow. In addition, the occurrence of the reaction N(2D) + N2O → NO(B2Πr) + N2 (X1Σ+g) has been verified. Finally we have observed emission at 3344 Å, which we attribute to the NF(A3Π), which has not been previously reported.  相似文献   

2.
The continuous absorption spectrum of molecular bromine has been examined using laser induced photodissociation spectroscopy. In this technique, Br2 molecules are photolyzed using a flashlamp-pumped dye laser; the atomic products of the dissociation are then monitored by time-resolved resonance absorption spectroscopy in the vacuum ultraviolet. The relative absorptivities for the transitions B3Πo+u ← X1Σ+g and 1Π1u ← X1Σ+g have been obtained at 18350, 21010 and 22125 cm−1.  相似文献   

3.
Rotational-state distributions of the CO+ (A–X, B–X) and N2+(B–X) emissions produced by the collisions of He(2 3S) with CO and N2 were studied in the collision energy (ER range 100–200 meV. The rotational populations of the emitting states can be fitte by single Boltzmann temperatures (TR. The TR (320 ± 30 K) for the ν′ = 3 and 4 levels of the CO+ (A2Π) state are nearly independent of, or slightly increase with, ER, while TR for the CO+(B2Σ+, ν′ = 0) state increases rapidly with ER.The TR (430 ± 20 K) for the N2+(B2Σ+, ν′ = 0) state is nearly independent or slightly decreases with increasing ER. Interactions providing these trends are discussed.  相似文献   

4.
Absorption and fluorescent scattering of nitrogen laser radiation by a low-pressure RF laboratory plasma (ne = 1012 cm−3) has been observed for the first negative system of N2+. A 67±1 ns lifetime of N2+ (B 2Σu+) was experimentally measured from the laser-induced fluorescence. In addition, enough collisionally excited N2 (B 3Πg) was produced to observe laser-induced fluorescence for the second positive system of N2. The lifetime of N2 (C 3Πu) was found to be 41±2 ns. The measured lifetimes are in good agreement with published values calculated from theory.  相似文献   

5.
Three-dimensional trajectory surface hopping calculations were performed on two diabatic energy surfaces. The covalent surface describes the K(2S) + O2(3Σg) state and the ionic surface K+(1S) + O2(2Πg). Transitions from one surface to another were computed through the Landau—Zener model. At small deflection angles, the energy loss distribution exhibits two peaks, as observed, due to O2 in its electronic ground state and to vibrationally excited O2.  相似文献   

6.
R. Polk  J. Fi er 《Chemical physics》2003,290(2-3):177-188
The electric field gradients (EFG’s) at the nucleus are calculated as a function of internuclear separation in the X2Σg+ and B2Σu+ electronic states of the nitrogen molecule cation using the internally contracted multireference configuration interaction (icMRCI) method. The EFG’s and potential energy functions (PEF’s) are used to estimate the 14N nuclear quadrupole coupling constants (NQCC’s) in the two electronic states as functions of vibrational and end-over-end rotational quantum numbers. The dependences of the computed constants on the basis set and reference configuration space are investigated. Since no counterpart for comparison of the calculated NQCC’s exists, the N2+ results are supported by analogous calculations on the X1Σg+ and A3Σu+ states of N2, for which established data are available. The overall good quality of the icMRCI wave functions is further corroborated by a favorable agreement of spectroscopic constants derived from the corresponding PEF’s and experimental data. Variations of the EFG with internuclear separation are explained in terms of wave function composition, and used for gaining specific insight into the chemical bonding in N2+ and N2.  相似文献   

7.
Measurements of electron stimulated desorption (ESD) yields of O, at incident electron energies below 20 eV, from 0.15 monolayers (ML) of O2 physisorbed at 20 K on a variety of molecular solids have been performed. It is observed that for O2 condensed on 4 ML of H2O, the O signal from dissociative electron attachment (DEA) to O2 is entirely absent. We attribute this to a complete quenching of the dissociative 2Πu, 2Σ+g, and 2Σ+u, resonances of O2 by the adjacent water molecules.  相似文献   

8.
Autoionizing Rydberg levels of Li2 molecules in a supersonic molecular beam are populated by stepwise excitation with two tunable pulsed dye lasers. The observed autoionization spectra show severe perturbations. Based on calculations of quantum defects and a perturbation treatment of l-uncoupling a tentative assignment of Rydberg series up to n = 32 is proposed. The convergence limits of these series yield a value of IP = 41475 cm−1 for the adiabatic ionization potential and a vibrational constant ωe = 263 cm−1 for the X2Σ+g ground state of Li+2. The experimental results are compared with ab initio calculations combined with a core polarization potential, which yield the potential curve. the dissociation energy, the quadrupole moment and the vibrational frequency for the X2Σ+g ground state of Li+2, in the excellent agreement with experimental findings.  相似文献   

9.
Large-scale ab initio coupled cluster and multi-reference configuration interaction calculations (MRD-CI) are carried out to determine the equilibrium geometry and the vertical electronic spectrum of linear C5+. Contrary to prior theoretical estimates we find three low-lying states within an energy range of 0.3 eV: 2Σu+, 2Σg+ and 2Πg and a symmetric arrangement of nuclei. Transitions from 2Σu+ to these low-lying states are dipole-allowed; sizeable oscillator strengths are computed for the 2Π+g←X2Σu+ transition at 2.62 eV and the 2Σg←X2Σu+ transition at 3.36 eV and should give a guide to spectroscopic identification of linear C5+.  相似文献   

10.
The radiative lifetimes of nine vibrational levels of the C3(1Πu) radical were obtained from decay time studies of the C3(1Πu1Σ+g) fluorescence induced by a tunable dye laser. The lifetimes of the different vibronic levels were found to be constant within the experimental error limits, namely, τo = (200 ± 10) ns. The collisional deactivation of the C3(1Πu) states by helium gives rate constants between 2.5 and 4 in 10−11 cm3 molecule−1 s−1 units.  相似文献   

11.
The 4067 Å line of the krypton-ion laser covers two transitions in the BO+u-X O+g system of 130Te2, R(36) in the 16-0 band and R(172) in the 18-0 band. Subsequent fluorescence has been recorded by Fourier transform spectrometry in the range 5900 to 15000 cm−1. Many transitions, with v' in the range 0 to 47, have been assigned to a new system, B O+u-b1+g, and vibrational and rotational constants for the new state have been derived. The value of Te for b Ig+ is about 9600.2 cm−1.  相似文献   

12.
用一束波长为360.55 nm的激光直接作用于超声射流的N2O分子束, 通过(3+1)共振增强多光子电离(REMPI)过程制备纯净的N2O+(X2П(0,0,0))母体离子, 再用另一束波长在243-278 nm范围的激光将母体离子激发至B2П态后解离. 扫描解离激光波长, 监测NO+离子碎片的强度, 从而获得N2O+离子B2П态的光致碎片激发(PHOFEX)谱. 通过拟合转动分辨光谱, 得到了相应的转动常数和自旋分裂常数, 从而区分了A2Σ+态高振动能级和B2П态带源的贡献, 明确了N2O+离子B2П态的光谱"带头"位置(37154 cm-1), 并将获得的振动光谱初步归属为B2П(v1,v2,v3)←X2П的振动跃迁序列. 通过对NO+碎片离子的飞行时间质谱峰形的分析, 还获得了解离过程中释放的平均平动能, 并结合电子激发态势能面, 讨论了N2O+离子B2П态的解离机理.  相似文献   

13.
A laser pulse-and-probe method has been used to determine the nascent vibrational populations in NO(v=0–4) and O2(v=6–11) formed in the thermal reaction: O(3P) + NO2 → O2(v) + NO(v). A frequency-tripled Nd: YAG laser is used to photolyse NO2, diluted tenfold in Ar, and laser-induced fluorescence spectroscopy in the NO A 2Σ+-X 2Π and O2 B 3Σu -X 3Σg electronic band system is used both to follow the kinetics of individual vibrational states and to determine the nascent vibrational distributions. The majority of the NO product is formed in v = 0 and the average vibrational yield is ≈ 4.6%. The O2 populations fall monotonically from v = 6 to 11 in a distribution close to what is expected on prior grounds. Based on a surprisal analysis, the average vibrational energy yield in O2 is ≈ 26%. The nature of the reaction dynamics is discussed.  相似文献   

14.
Absolute kinetic energy distributions and yields associated with ground state 3P and excited state 1D oxygen atoms have been obtained for O anion electron stimulated desorption from condensed O2 in the electron energy range 6–15 eV. The observed yields are understood as resulting essentially from dissociative electron attachment reactions via the two lowest 2Σ+g O2 resonance states through adiabatic and non-adiabatic transitions to the limits O(2P) + O(3P) and O(2P) + O(1D). The kinetic energy distributions show the prominent role of electron multiple collision processes and post-dissociation interactions of the O anions in the condensed phase.  相似文献   

15.
Saddle point geometries and barrier heights have been calculated for the H abstraction reaction HO2(2A″)+H(2S) → H2(1Σ+g)+O2(3Σg) and the concerted H approach-O removing reaction HO2 (2A″)+H(2S) → H2O(1A1)+O(3P) by using SDCI wavefunctions with a valence double-zeta plus polarization basis set. The saddle points are found to be of Cs symmetry and the barrier heights are respectively 5.3 and 19.8 kcal by including size consistent correction. Moreoever kinetic parameters have been evaluated within the framework of the TST theory. So activation energies and the rate constants are estimated to be respectively 2.3 kcal and 0.4×109 ℓ mol−1 s−1 for the first reaction, 20.0 kcal and 5.4.10−5 ℓ mol−1 s−1 for the second. Comparison of these results with experimental determinations shows that hydrogen abstraction on HO2 is an efficient mechanism for the formation of H2 + O2, while the concerted mechanism envisaged for the formation of H2O + O is highly unlikely.  相似文献   

16.
A hollow cathode combined with a corona excited supersonic expansion has proven to be an efficient method of producing a stable discharge in a N2/Ar gas mixture. A high-resolution and rotationally cold absorption spectrum of the well-known (2,0) and (8,7) bands of the B3Πg ← A3Σu+ first positive system of N2 was recorded. It illustrates the sensitivity of the laser optogalvanic detection technique coupled to such an apparatus. A significant reduction of the linewidth and an enhancement of the signal-to-noise ratio were obtained. A high variational excitation process has been observed and is discussed.  相似文献   

17.
A high-resolution (1–7 meV) threshold photoelectron spectroscopic study of IBr was performed using synchrotron radiation and a penetrating-field electron spectrometer over the valence ionization region of the molecule. Extensive vibrational structure was found in all three electronic-state band systems (X2Πi, A2Πi and B2Σ+) of IBr+. In the (X2Πi) band system both spin–orbit components exhibited extended vibrational structure in the Franck–Condon gap regions that is attributed to resonance autoionization of neutral Rydberg states lying in these energy regions. Analysis of this vibrational structure yielded accurate spectroscopic constants.  相似文献   

18.
Relative emission spectra for the bent to linear, CO2(1B2)---CO2(X1Σ+g) transitions have been calculated using the model: harmonic oscillator, symmetric-top wavefunctions and energy levels for CO2(1B2); first-orer Fermi resonance vibrational wavefunctions and energy levels for CO2(X1Σ+g); a Boltzmann distribution of vibrational and rotational states in CO2(1B2); and a constant electronic transition moment. With the literature CO2(1B2) molecular structure, spectra calculated using this model show characteristics similar to the low-temperature chemiluminescence from the combination of atomic oxygen and carbon monoxide. The calculated spectra account for experimental band positions to wavelengths of 570 nm and the weak dependence of the spectra on temperature over the range 206–353 K. The latter result was obtained from a CO2(1B2) bending fundamental of 600 cm−1. The calculated spectra also show a violet-shift in intensity and an attenuated band structure at higher temperatures. The magnitude of these effects depends on the CO2(1B2) force constants and not on the CO2(1B2) molecular structure.  相似文献   

19.
在超声分子束条件下,利用360.50 nm的电离激光使N2O分子经由[3+1]共振增强多光子电离(REMPI)产生纯净的N2O+(X2Π(000))分子离子,用另一束解离激光在230-275 nm范围扫描获得N2O+经由B2Πi←X2Π跃迁产生的光解碎片(NO+和N2+)激发(PHOFEX)谱.获得的光解碎片激发谱可以归属为B2Πi(00n)←X2Π(000)序列跃迁.我们分别将线性三原子分子离子N2O+中N―N伸缩振动简化成NO和N之间的简谐振动,N―O伸缩振动简化成N2和O之间的简谐振动,用谐振子的简谐势能曲线和波函数对N2O+分子离子X2Π和B2Πi电子态振动能级间跃迁的Franck-Condon因子进行计算,和实验得到的碎片离子增强谱实验强度进行比较,对前人给出的分子数据(分子平衡核间距)进行验证,讨论了N2O+经由B2Πi(00n)←X2Π(000)电子态跃迁的光解离机理和碎片离子的分支比.  相似文献   

20.
Large-scale MRD CI calculations assign to AlP the ground state X 3Σ (9σ22) and a close-lying state 1 3Π (9σ3π3) (Te = 0.08 eV). Up to transition energies of 2.0 eV, other states are described by the configurations 9σ3π3 (11Π), 8σ24 (1 1Σ+), 9σ22 (1 1Δ and 2 1Σ+) and 9σ3π24π (1 5Π). The 2 3Π state, located at ≈ 2.30 eV, shows a shallow double minimum. Numerous perturbations are expected to induce predissociation upon 2 3Π. Multiplets arising from the occupation 8σ234π are clustered in the 3.25–3.50 eV region. Quintet states with the configuration 8σ9σ3π34π are bound, with Te values (in eV) of 3.80 (1 5Σ+), 4.44 (1 5Δ) and 4.88 (3 5Σ), respectively. The 9σ → 4s Rydberg members 5Σ and 3Σ lie in the 4.58–4.72 eV energy region. The first ionization potential (ionization to X4Σ of AlP+, 9σ → ∞) is estimated to be 7.65 eV. Ionization to the 1 2Σ and 1 2Π states of AlP+ is suggested to occur between 8.0 and 8.8 eV. The dipole moments of X 3Σ, 1 1Δ and 2 1Σ+ are close to 1.0 D, whereas the 1 1Σ+ state has μ = 3.49 D; 1 3Π and 1 1Π have dipole moments from 2.45 to 2.91 D. All low-lying states show a polarity Al+P. Finally, the electronic structure and transition energies of AlP are compared with those of the isoelectronic species BN, AIN, and SiP+.  相似文献   

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