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1.
S. A. Pozdneev 《Journal of Experimental and Theoretical Physics》2004,99(5):915-933
The main features of resonance scattering of electrons by molecules are described and resonances are determined on the basis of the theory of collisions in a two-body system, as well as resonances emerging as a result of collisions in a few-body system. Regularities in the emergence of such resonances and their characteristics are analyzed. The results of calculations of these resonant processes occurring during collisions of electrons with diatomic molecules, made on the basis of the quantum theory of scattering in a few-body system, are presented. The results of calculating the cross sections of resonant processes of electron collisions with molecules are compared with the available experimental data and with the results of calculations based on other approximations. 相似文献
2.
Sergey Pozdneev 《Journal of Russian Laser Research》2017,38(2):107-123
We describe the main features of resonances in scattering, determining the resonances in view of the theory of collisions in a two-body system, as well as the resonances emerging as a result of collisions in a few-body system. We analyze regularities in the emergence of such resonances and their characteristics. We discuss the results of calculations of the resonant processes occurring during collisions of electrons with diatomic molecules, in view of the quantum theory of scattering in a few-body system based on the Faddeev–Yakubovsky equations. 相似文献
3.
We study the spontaneous dissociation of diatomic molecules produced in cold atomic gases via magnetically tunable Feshbach resonances. We provide a universal formula for the lifetime of these molecules that relates their decay to the scattering length and the loss rate constant for inelastic spin relaxation. Our universal treatment as well as our exact coupled channels calculations for 85Rb dimers predict a suppression of the decay over several orders of magnitude when the scattering length is increased. Our predictions are in good agreement with recent measurements of the lifetime of 85Rb(2). 相似文献
4.
Hummon MT Tscherbul TV Kłos J Lu HI Tsikata E Campbell WC Dalgarno A Doyle JM 《Physical review letters》2011,106(5):053201
We present an experimental and theoretical study of atom-molecule collisions in a mixture of cold, trapped N atoms and NH molecules at a temperature of ~600 mK. We measure a small N+NH trap loss rate coefficient of k(loss)(N+NH)=9(5)(3)×10(-13) cm(3)?s(-1). Accurate quantum scattering calculations based on ab initio interaction potentials are in agreement with experiment and indicate the magnetic dipole interaction to be the dominant loss mechanism. Our theory further indicates the ratio of N+NH elastic-to-inelastic collisions remains large (>100) into the mK regime. 相似文献
5.
We report the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary parts of the index of refraction n for argon, krypton, and xenon as a function of the gas density for several velocities of the lithium beam. The linear dependence of (n-1) with the gas density is well verified. The total collision cross section deduced from the imaginary part of (n-1) is in very good agreement with traditional measurements of this quantity. Finally, the real and imaginary parts of (n-1) and their ratio rho exhibit glory oscillations, in good agreement with calculations. 相似文献
6.
Cold inelastic collisions between confined cesium (Cs) atoms and Cs2 molecules are investigated inside a CO2 laser dipole trap. Inelastic atom-molecule collisions can be observed and measured with a rate coefficient of approximately 2.6 x 10(-11) cm3 s(-1), mainly independent of the molecular rovibrational state populated. Lifetimes of purely atomic and molecular samples are essentially limited by rest gas collisions. The pure molecular trap lifetime ranges 0.3-1 s, 4 times smaller than the atomic one, as is also observed in a pure magnetic trap. We give an estimation of the inelastic molecule-molecule collision rate to be approximately 10(-11) cm3 s(-1). 相似文献
7.
Ultracold collisions between Cs atoms and Cs2 dimers in the electronic ground state are observed in an optically trapped gas of atoms and molecules. The Cs2 molecules are formed in the triplet ground state by cw photoassociation through the outer well of the 0-(g) (P3/2) excited electronic state. Inelastic atom-molecule collisions converting internal excitation into kinetic energy lead to a loss of Cs2 molecules from the dipole trap. Rate coefficients are determined for collisions involving Cs atoms in either the F=3 or F=4 hyperfine ground state, and Cs2 molecules in either highly vibrationally excited states (nu'=32-47) or in low vibrational states (nu'=4-6) of the a3 summation(u)+ triplet ground state. The rate coefficients beta approximately 10(-10) cm3/s are found to be largely independent of the vibrational and rotational excitation indicating unitary limited cross sections. 相似文献
8.
Hanford AD O'Connor PD Anderson JB Long LN 《The Journal of the Acoustical Society of America》2008,123(6):4118-4126
In the current study, real gas effects in the propagation of sound waves are simulated using the direct simulation Monte Carlo method for a wide range of frequencies. This particle method allows for treatment of acoustic phenomena at high Knudsen numbers, corresponding to low densities and a high ratio of the molecular mean free path to wavelength. Different methods to model the internal degrees of freedom of diatomic molecules and the exchange of translational, rotational and vibrational energies in collisions are employed in the current simulations of a diatomic gas. One of these methods is the fully classical rigid-rotor/harmonic-oscillator model for rotation and vibration. A second method takes into account the discrete quantum energy levels for vibration with the closely spaced rotational levels classically treated. This method gives a more realistic representation of the internal structure of diatomic and polyatomic molecules. Applications of these methods are investigated in diatomic nitrogen gas in order to study the propagation of sound and its attenuation and dispersion along with their dependence on temperature. With the direct simulation method, significant deviations from continuum predictions are also observed for high Knudsen number flows. 相似文献
9.
We present a theoretical study of atom-molecule collisions in superimposed electric and magnetic fields and show that dynamics of electronic spin relaxation in molecules at temperatures below 0.5 K can be manipulated by varying the strength and the relative orientation of the applied fields. The mechanism of electric field control of Zeeman transitions is based on an intricate interplay between intramolecular spin-rotation couplings and molecule-field interactions. We suggest that electric fields may affect chemical reactions through inducing nonadiabatic spin transitions and facilitate evaporative cooling of molecules in a magnetic trap. 相似文献
10.
11.
We report variational calculations of the equation of state of hot and cold, nuclear and neutron matter. The calculations cover a wide density range of interest in heavy-ion collisions and astrophysics. The “hot” calculations are limited to temperatures less than 20 MeV. A realistic nuclear hamiltonian that contains two- and three-nucleon interactions and fits the nucléon-nucléon scattering, as well as nuclear matter data, is used. Neutron star structure calculations are reported and their sensitivity to the three-neutron interactipn is examined. The liquid-vapor phase equilibrium, as well as the behavior of the effective mass in nuclear matter is discussed. 相似文献
12.
We present a systematic understanding of the rotational structure of a long-range (vibrationally highly-excited) diatomic molecule. For example, we show that depending on a quantum defect, the least-bound vibrational state of a diatomic molecule with -C
n
/r
n
(n > 2) asymptotic interaction can have only 1, 2, and up to a maximum of n-2 rotational levels. A classification scheme of diatomic molecules is proposed, in which each class has a distinctive rotational structure and corresponds to different atom-atom scattering properties above the dissociation limit.Received: 15 June 2004, Published online: 28 September 2004PACS:
33.15.Mt Rotation, vibration, and vibration-rotation constants - 34.10. + x General theories and models of atomic and molecular collisions and interactions (including statistical theories, transition state, stochastic and trajectory models, etc.) - 03.75.Nt Other Bose-Einstein condensation phenomena - 03.75.Ss Degenerate Fermi gases 相似文献
13.
We present the first measurement of a photoassociative spectrum of an alkaline earth element near the dissociation limit. The observed spectrum of Ca2 formed from cold atoms shows the regular vibrational series with the characteristic spacing of the 1/R3 asymptotic potential. The interpretation is in principle simplified compared to previous measurements on alkali metals by the nondegenerate ground state and the missing hyperfine structure of 40Ca. As an example, we derive the natural decay rate of the excited atomic 4p 1P1 state from the positions of the observed vibrational and rotational resonances with reduced uncertainty compared to previous measurements. 相似文献
14.
Derivation of a temperature-dependent accommodation coefficient for use in modeling laser-induced incandescence of soot 总被引:1,自引:0,他引:1
H. A. Michelsen 《Applied physics. B, Lasers and optics》2009,94(1):103-117
This paper presents a derivation of an expression to estimate the accommodation coefficient for gas collisions with a graphite
surface, which is meant for use in models of laser-induced incandescence (LII) of soot. Energy transfer between gas molecules
and solid surfaces has been studied extensively, and a considerable amount is known about the physical mechanisms important
in thermal accommodation. Values of accommodation coefficients currently used in LII models are temperature independent and
are based on a small subset of information available in the literature. The expression derived in this study is based on published
data from state-to-state gas-surface scattering experiments. The present study compiles data on the temperature dependence
of translational, rotational, and vibrational energy transfer for diatomic molecules (predominantly NO) colliding with graphite
surfaces. The data were used to infer partial accommodation coefficients for translational, rotational, and vibrational degrees
of freedom, which were consolidated to derive an overall accommodation coefficient that accounts for accommodation of all
degrees of freedom of the scattered gas distributions. This accommodation coefficient can be used to calculate conductive
cooling rates following laser heating of soot particles. 相似文献
15.
E.E. Nikitin 《Molecular physics》2013,111(4):389-396
The transition complex method is used for calculating the rate constant of non-adiabatic vibrational deactivation of diatomic molecules in the 2II electronic state upon collisions with inert gas atoms. The main contribution to the rate constant comes from vibronic transition caused by spin-orbital and orbital-rotational couplings. The two-dimensional Landau-Zener approximation is considered in connection with calculation of the nonadiabatic transition near the crossing line of two potential surfaces, and the limitations of ideas concerning the activated complex are discussed. The general expression for the rate constant derived from the diatomic molecule-atom collision is correlated with that for the atomic collision. 相似文献
16.
DISTORTED WAVE-WAVE PACKET APPROACH TO VIBRATIONAL DEACTIVATION OF DIATOMIC MOLECULE BY COLLISIONS WITH SOLID SURFACE
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A model is proposed for vibrational dexcitation of diatomic molecule by collisions with a solid surface, and used to predict the rotational and translational energy distributions and other properties of interest. It is found that molecular rotation dominates over translation in receiving the vibrational energy released, even for the heavier diatomic molecules. 相似文献
17.
Vladimir A. Sautenkov Sergey A. Saakyan Alexander M. Akulshin Mikhail A. Gubin Vladimir N. Kuliasov Boris B. Zelener 《Journal of Russian Laser Research》2013,34(4):375-378
We study Doppler-free saturation resonances in the absorption band $ {{\mathrm{B}}^1}{\Pi_{\mathrm{u}}}-{{\mathrm{X}}^1}\Sigma_{{^{\mathrm{g}}}}^{+} $ of rubidium diatomic molecules in the frequency range near the D2 line of lithium atoms (671 nm). We observe contrast saturation resonances and record a variation in the laser light transmission of 4% due to optical saturation. The large optical nonlinearities in the molecular diatomic gas can be used for investigating the four-wave mixing and other nonlinear effects. 相似文献
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19.
We present a detailed analysis of near zero-energy Feshbach resonances in ultracold collisions of atom and molecule,taking the He–PH system as an example, subject to superimposed electric and magnetic static fields. We find that the electric field can induce Feshbach resonance which cannot occur when only a magnetic field is applied, through couplings of the adjacent rotational states of different parities. We show that the electric field can shift the position of the magnetic Feshbach resonance, and change the amplitude of resonance significantly. Finally, we demonstrate that, for narrow magnetic Feshbach resonance as in most cases of ultracold atom–molecule collision, the electric field may be used to modulate the resonance, because the width of resonance in electric field scale is relatively larger than that in magnetic field scale. 相似文献
20.
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