共查询到20条相似文献,搜索用时 31 毫秒
1.
碰撞反应Ca+C2H5Br和Ca+nC3H7Br产物CaBr的内能态分布 总被引:1,自引:0,他引:1
采用准经典轨线方法研究了碰撞反应Ca+C2H5Br和Ca+nC3H7Br产物CaBr的内能态分布,计算了产物分子CaBr的平均振动、转动和平动能量以及总可资用能量.结果表明,当碰撞能为7.54kJ/mol时,产物的能量主要为振动能量;随着碰撞能增加,产物的平动能和转动能增加,而振动能略微减小,最可几振动态向较低振动能级移动;反应物分子内能态分布对产物分子的内能态分布影响很小;反应基团越大,产物的振动能占总可资用能量的比例就越高.碰撞反应Ca+C2H5Br和Ca+nC3H7Br均存在两条竞争的反应路径迁移相碰和直接反应路径.前者产生高振动激发态产物CaBr,后者引起C-Br键断裂.当碰撞能增加时,两种反应均倾向于后者. 相似文献
2.
利用积分时间分辨荧光光谱方法,研究了RbH(X1∑+,v=0~2)与H2间的振动碰撞能量转移.在Rb-H2混合样品池中,泵浦激光双光子激发Rb原子至6D态,Rb(6D)与H2反应生成RbH(x1∑+)分子,探测激光延迟泵浦激光20 ns,通过激光感应荧光光谱(LIF)的测量,确定了X1∑+(v=0~2,J)原生态的转动... 相似文献
3.
Zhaunerchyk V Al-Khalili A Thomas RD Geppert WD Bednarska V Petrignani A Ehlerding A Hamberg M Larsson M Rosen S van der Zande WJ 《Physical review letters》2007,99(1):013201
We have studied the dissociative recombination (DR) of molecular hydrogen ions with slow electrons over a range of collision energies from 0 to 400 meV. By employing a pulsed expansion source for rotational cooling and by exploiting super elastic collisions with near-0-eV electrons in a heavy ion storage ring for vibrational cooling, we observe a highly structured DR cross section, comparable to that reported for HD+. Using para-hydrogen-enriched ion beams, we identify for the first time features in the DR cross sections attributed to nu=0, J=even molecules (para-H2) and nu=0, J=odd (ortho-H2) molecules, separately. Indications are given that para levels have different DR rate coefficients from ortho levels for the first four vibrational levels at near-0-eV collisions. 相似文献
4.
A number of processes in which highly excited states of atoms and molecules participate are investigated. These processes are of interest for the kinetics of a low-temperature plasma, for atomic and molecular spectroscopy, and for astrophysics. A quasiclassical theory is developed for transitions between Rydberg states with change of the principal quantum number, and also for the processes of direct and associative ionization of highly excited atoms, which result from collisions between a neutral particle and its atomic core. The state of the inner electrons of a quasimolecular (molecular) ion is not altered by transitions of the outer electrons. Specific calculations are carried out for the case of the collision of hydrogen H(n) with helium He (1s2) atoms. It is shown that the cross sections and the rate constants of these processes are determined in this case by the mechanism investigated in the paper, and not by scattering of the Rydberg electron by the neutral particle. The cross sections for dipole excitation and dissociation of molecular ions from high vibrational energy levels by electron impact is calculated in the Born-Coulomb approximation. The cross sections and the rates of dissociative and three-particle attachment of electrons to ions are determined. The processes of autoionization and autodissociation decay of Rydberg states of vibrationally excited molecules are determined. Also investigated are radiative transitions near the dissociation limit of diatomic molecular ions and neutral molecules, viz., photodissociation and radiative decay of high vibrational levels, and photodissociation and translational (inverse-bremsstrahlung) absorption in collision of atomic particles.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. Lebedeva AN SSSR, Vol. 145, pp. 80–130, 1984. 相似文献
5.
Abstract Intensities and decay rates of delayed fluorescence initiated by CO2 laser excitation of the triplet-state molecules are used to probe collisional relaxation of vibrationally excited polyatomic molecules. Collisional efficiencies for large polyatomic molecules are found not to exceed the value of 10?2-10?3 even in most favourable case of vibrational energy exchange in collisions between parent molecules. At intermediate levels of excitation (1500—12000 cm?1) the average energies <ΔE> transferred per collision with polyatomic molecules increase as vib>rn, where m≥2, and decrease with increasing numbers of atoms in the excited molecules. 相似文献
6.
The temporal evolution for individual rovibrational levels of the B state of the iodine molecule is observed by two-photon delayed spectroscopy. In particular the rotational energy transfer (RET) process due to collisions of the molecules in the B state with molecules in the ground state is studied. Thermal averaged rate constants for pairs of rotational levels of the v=27 vibrational state are measured. The results are discussed in terms of the dynamics of the collision process and numerical fits to the most important parametric fitting laws for RET are presented. 相似文献
7.
Nikolov AN Ensher JR Eyler EE Wang H Stwalley WC Gould PL 《Physical review letters》2000,84(2):246-249
We have developed a two-step " R-transfer" method that efficiently produces translationally ultracold potassium molecules in the X (1)Sigma(+)(g) electronic ground state. Laser-cooled atoms are initially photoassociated at large internuclear separation R to form molecules in high vibrational levels of the 1 (1)Pi(g) state, which are in turn excited by an additional laser to shorter-range Rydberg states such as 5 (1)Pi(u) and 6 (1)Pi(u). Subsequent radiative decay produces ground-state molecules at rates up to 10(5) molecules/second per vibrational level. 相似文献
8.
B. Stevens 《Molecular physics》2013,111(6):589-596
The transfer of vibrational energy from molecules of β-naphthylamine excited by the mercury lines at 2804 Å and 2652 Å to the homologous series of paraffin hydrocarbons up to n-hexane has been investigated in the gas phase at 180°C. Although the average amount of energy transferred collisionally increases with the complexity of the added gas by a factor of 5, the transfer efficiency expressed as an accommodation coefficient remains virtually unchanged. A transfer mechanism based on the internal redistribution of vibrational energy within the collision complex is examined, in terms of which it is unnecessary to invoke vibration-vibration transfer except for pentane and hexane. The collision duration estimated on the basis of this model is well within an order of magnitude of that expected from collision diameters and relative velocities of the molecules concerned. 相似文献
9.
D.C. Clary 《Molecular physics》2013,111(6):1295-1310
A quantum-dynamical method is described for investigating the translational-vibrational energy transfer that occurs in the collinear collision of an atom with a linear triatomic molecule. The technique is applied to the computation of vibrational transition probabilities for the collinear collisions of helium atoms with CO2, OCS and HCN over a range of energies. Realistic potentials are used for the triatomic molecules while simple exponential or Morse potentials are used to describe the helium-molecule interaction. The effects of varying the atomic masses and the potential function parameters are examined. It is found, that the symmetric stretch vibrational modes of CO2, OCS and HCN are preferentially excited (or relaxed), by collision with the atom, over the asymmetric stretch modes. 相似文献
10.
The collisional excitation of the lower vibrational levels of
H2(1Σg+) molecules by low-energy electron impact is
computed using an empirical model potential and by solving the
coupled-channels scattering equations within a space-fixed (SF)
frame of reference formulation. Numerically converged partial,
integral inelastic and elastic cross-sections are obtained from what
is an essentially exact treatment of the dynamics and the results
are compared with measurements and with earlier calculations on the
same system. The usefulness of the SF method for handling excitation
processes at near-threshold collision energies is discussed and
analyzed through the calculations of collisional superelastic
partial cross-sections down to 10-2 meV of collision energy. 相似文献
11.
Through quantum-beat spectroscopy collision relaxation of a high vibrational level of SO2 at 44 877.52 cm(-1) is characterized. This is a first measurement of collision relaxation for a single, highly excited vibrational level. The deduced relaxation cross section of this excited level by Ar is 216 A(2), 5 times the area of the hard sphere, and by an ambient temperature SO2 molecule is 969 A(2), almost 20 times the hard sphere. These cross sections indicate that relaxation collisions of highly vibrationally excited molecules have effective distances much longer than van der Waals radii and involve mechanisms qualitatively different from lower excitations. 相似文献
12.
Roger L. Wilkins 《Molecular physics》2013,111(2):555-564
Rate coefficients are calculated for the reactions of H and D-atoms with vibrationally excited HF and DF molecules. Three-dimensional classical trajectories of the collision dynamics of these reactions have been calculated by means of the London-Eyring-Polanyi-Sato (LEPS) potential energy surface. The Monte Carlo procedure is used to start each collision trajectory. Results of this study indicate that (a) chemical exchange provides an efficient mechanism for relaxing vibrationally excited HF and DF molecules by H and D-atoms; (b) multiple-quantum transitions are important in the deactivation processes; and (c) both vibration-translation and vibration-rotation energy transfers contribute to vibrational relaxation of vibrationally excited HF and DF molecules by H and D-atoms. The vibrational relaxation of HF (v = 1) by H-atoms is faster than the vibrational relaxation of DF (v = 1) by H-atoms. A similar effect is indicated for D-atoms; i.e. the vibrational relaxation of DF (v = 1) by D-atoms is faster than the vibrational relaxation of HF (v = 1) by D-atoms. Room temperature vibration to translation-rotation (V → T, R) relaxation rates in units of (μsec Torr)-1 are as follows: 13·8 × 10-2 for HF (v = 1) by H, 3·1 × 10-2 for DF (v = 1) by D, 5·5 × 10-3 for HF (v = 1) by D, and 1·9 × 10-2 for DF (v = 1) by H. Rates of deactivation of vibrationally excited HF and DF molecules by H and D-atoms are very fast. Rate coefficients are provided for many reactions that have not been measured experimentally. 相似文献
13.
In this second part of the in [l] started paper the results of microphysical determined collision frequencies of the electrons for the excitation and ionization of metastable molecules, excited in electronic states, and of the energy loss rates of the electrons due to elastic collisions, vibrational excitation, electronic excitation, dissociation and ionization of the molecules in a N2 - H2 -plasma are represented and discussed. These investigations are related to a low ionized, homogeneous and stationary plasma in a mixture and are performed for the range 6- 100 V/(cm Torr) of the reduced electric field strength and for any composition of the N2 - H2-mixture. 相似文献
14.
《Surface science》1996,366(3):L750-L754
Using the REMPI technique we have studied the internal state distribution of deuterium molecules produced by the interaction of atomic deuterium with chemisorbed deuterium on Ni(110) at 180 K. We observed molecules in vibrational states up to v = 3 with a mean vibrational energy of 220 meV. The mean rotational energies of the molecules in the vibrational states v = 0 to 3 are 185 meV, 133 meV, 75 meV and 37 meV, respectively. The overall mean rotational energy amounts to 150 meV, again far in excess of the mean rotational energy of molecules accommodated to the surface. The data are consistent with direct interactions of the impinging particles with the adsorbed particles (Eley-Rideal reaction and collision induced desorption), for which it is assumed that a considerable amount of the potential and kinetic energy of the impinging atoms is channeled into translational and internal energy of the reaction products. 相似文献
15.
A. I. Parkhomenko A. M. Shalagin 《Journal of Experimental and Theoretical Physics》1998,86(5):897-902
We derive a simple analytic formula that describes the relative difference of transport collision rates, Δv/v, for collisions of molecules and atoms in the rovibrational excitation of the former by light, as a function of the rotational
quantum numbers of the combining (i.e., affected by radiation) levels of the molecules. (The relative difference of transport
collision rates can be measured in light-induced drift, or LID, experiments and is proportional to the LID effect.) The formula
is valid in the energy sudden approximation and is based on the well-known factorization formula for cross sections of RT-transitions
in linear molecules that collide with atoms. We show that in this approximation the factor Δv/v is the sum of two independent terms, the vibrational term (Δv/v)vib and the rotational term (Δv/v)rot. Each term can be measured individually in LID experiments.
Zh. éksp. Teor. Fiz. 113, 1649–1660 (May 1998) 相似文献
16.
Properties of collision transfer of vibrational energy in the vibrational quasi-continuum of mixed singlet-triplet levels of anthraquinone are studied by the method of time-resolved delayed fluorescence. The two-exponential fluorescence decay is analyzed in the kinetic approximation. It is shown that dependences of the intensities and decay rates of the fast and slow components on pressure can be used for estimating the rates of the establishment of the vibrational (V-V) and thermal (V-T) equilibrium. The efficiency β and the average energy 〈ΔE〉 transferred in collisions are estimated for these processes. It is found that the V-V process is characterized by high values of β, which, however, are lower in the quasi-continuum of mixed singlet-triplet states than the gas-kinetic values (β < 0.2). The transformation of the vibrational energy to the translational energy occurs with the low efficiency (10?2 > β > 10?5). The average energy 〈ΔE〉 transferred during a collision in the V-V process is comparable with the energy predicted by the statistical theory of ergodic transfer. The correlation between experimental and theoretical values improves when the time resolution of the experiment is sufficient for the separation of the V-V and V-T processes. 相似文献
17.
Rybak L Amaran S Levin L Tomza M Moszynski R Kosloff R Koch CP Amitay Z 《Physical review letters》2011,107(27):273001
The formation of diatomic molecules with rotational and vibrational coherence is demonstrated experimentally in free-to-bound two-photon femtosecond photoassociation of hot atoms. In a thermal gas at a temperature of 1000 K, pairs of magnesium atoms, colliding in their electronic ground state, are excited into coherent superpositions of bound rovibrational levels in an electronically excited state. The rovibrational coherence is probed by a time-delayed third photon, resulting in quantum beats in the UV fluorescence. A comprehensive theoretical model based on ab initio calculations rationalizes the generation of coherence by Franck-Condon filtering of collision energies and partial waves, quantifying it in terms of an increase in quantum purity of the thermal ensemble. Our results open the way to coherent control of a binary reaction. 相似文献
18.
J. Franz F. A. Gianturco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):407-413
Vibrationally inelastic quantum calculations are carried
out at low collision energies for the scattering of a beam of
positrons off acetylene gaseous molecules. The normal mode analysis
is assumed to be valid and the relative fluxes into the C–C and C–H
symmetric vibrational modes are computed within a Body-Fixed (BF)
formulation of the dynamics by solving the relevant vibrational
Coupled Channels (VCC) equations. The clear dominance of the C–C
mode is observed near threshold and the implications of this finding
are briefly considered in relation to more global indicators like
the average vibrational energy transfer indices as obtained in the
present work. 相似文献
19.
基于文献[1],本工作在较高泵浦激光能通量范围,测量并研究了BCl3分子振动激发v_3吸收谱及时间演变,观察了v3激发弛豫的几种能量转移过程,以及对泵浦激光能量BCl3气压等参数的依赖关系。表明泵浦光脉冲产生一个振动态非热分布的系综,转动能量转移对引起这种非热分布有重要作用。用简化碰撞动力学模型讨论了BCl3振动激发吸收谱的演变过程,得到振动态再分布的简单关系;Pτv-v≌c/K′(Tv,T0,q)和等效振动温度、平均吸收光子数的分析表达式,与实验结果定性地符合。
关键词: 相似文献
20.
Shao-Chi Lin James H. Morris 《Journal of Quantitative Spectroscopy & Radiative Transfer》1977,17(5):577-593
The problem of multi-level absorption of i.r. laser radiation in polyatomic gases is examined using the density matrix formalism. The general condition under consideration is that field broadening effects are significant, but the detailed and discrete features of the absorption spectra remain very important. Collisional effects are taken into account through macroscopic relaxation terms, but the cumulative effects of collisional relaxation are assumed to cause only minor perturbations to the overall vibrational-rotational populations over the optical pumping time scale of interest. Various approximate formulae are then derived for locating the optimum frequency for optical pumping of three consecutive anharmonic vibrational levels within a given normal mode and for predicting the intensity- and frequency-dependence of the resultant uppermost level population density during a quasi-steady state balance among the absorption, stimulated emission, dephasing collision and rotational relaxation rates. Numerical examples are illustrated for pumping of the three lowest vibrational levels within the non-degenerate asymmetric stretching mode of the linear triatomic molecule CO2 for which the absorption spectra are relatively simple and well known. Some possible applications of these results to the problem of i.r. laser frequency conversion and to the interpretation of wavelength-selective i.r. photodissociation recently observed in many symmetric top molecules, such as BCl3, SiF4 and SF6 for which the absorption spectra are much more complex and the spectroscopic constants much less certain, are also discussed. 相似文献