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Hydrogen and inert gas atoms collisional excitation cross sections calculated by multistate impact parameter approximation
Energy transfer between molecules and excited atoms - quenching of excited argon atoms formed by beta radiation from tritium source and low energy electron impact
Parabolic coordinate evaluation of atomic form factor of hydrogen atom for excitation cross section induced by electron collision
Fast electron calculations for atomic hydrogen excited state ionization
Differential cross sections for Coulomb scattering of electrons without atomic excitation from thin aluminum targets for incident energies from 0.1 to 3.0 mev
We used the Dykhne formalism to develop an analytical model for correlated simultaneous ionization excitation process of two-electron helium-like atoms in a strong laser field, and then analyzed the contribution of recollision effect on transition rate in a linearly polarized laser field. Also, we briefly discussed recollision effect in a circularly and linearly polarized laser field. We were interested to examine how atomic excitation and recollision affect the transition rate because observations indicated the significance of both processes on the tunneling ionization of atoms in a linearly polarized laser radiation. We showed that, under the conditions considered here, the aforementioned effects play an important role and, therefore, must be taken into account in the case of a linear polarization, while the recollision effect do not affect the rate in a circular polarization.
We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number N of the atoms in the traps. Our method overcomes the problem of the {radical}(N) dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown N, and can be applied for single-atom loading of dipole traps and optical lattices.
The results from a semiclassical calculation of the thermal rate coefficient for the radiative association process H(n = 2) + H(n = 1) - H2 + hv are presented (n is the principal quantum number of the separated hydrogen atoms). The relative importance of this reaction in various environments is briefly discussed. Models of the early universe around the epoch of recombination and protostellar winds have been calculated which include the excited atom process. Not surprisingly, it is shown that the excited atom process will not be important in the general interstellar medium, except possibly in environments where the amount of Ly-alpha photon trapping is large. Examples may be the material surrounding quasars, active galactic nuclei, and bright H II regions. The most likely application of this process might be within rapidly evolving systems where a large transient n = 2 population of neutral hydrogen could result in a burst of molecular hydrogen formation.
This work continues a theoretical investigation of the capabilities of the well-known method based on using a monochromatic probe light beam in combination with optical pumping of atoms (molecules) of a rarefied-gas medium by a broadband radiation in a thin cell the diameter of which is much larger than its internal thickness. In contrast to calculations carried out in the previous publications on this method of spectroscopy, here, we consider the case of arbitrary values of pump intensity and thickness of a cylindrical gas cell. Thus, all the possible mechanisms and specificities of velocity selection of atoms in optically excited levels caused by transit-time relaxation of such atoms in gas cells of this kind are analyzed. Within the framework of this approach, sub-Doppler absorption resonances of the probe light beam corresponding to quantum transitions from the upper level excited by optical pumping are investigated. The obtained results can be used in high-resolution spectroscopy of atoms (molecules), as well as for laser-frequency stabilization to established narrow spectral resonances.
Coulomb scattering cross section for electrons without atomic excitation and energy of 1 mev incident on thin aluminum foil
Numerical calculation of electron atom excitation and ionization rates
It is assumed that, the atomic excitations probability can be calculated using first order perturbation theory and dipole approximations. The validity of the dipole approximations had been examined by comparing the results with the results obtained by exact calculations within the first order perturbation theory[2]. Figure 1 shows the time dependence of the transition probability in the dipole approximation. From these plots it is obvious that, the probabilities obtained in the length gauge are higher than that in the velocity gauge, in the interaction period (−τ/2<t<τ/2). After passing this time interval, transition probabilities for these two gauges became equal to each other precisely. Moreover those results are equal to the corresponding exact (without the dipole approximation) calculations results. (Figure 2) Though the time evolution of the same transition probabilities are different for these cases, the final results are the same for all three cases, excluding the 6s-6p{sub 0} transition. For the later case, only the length gauge give a false results, but the velocity gauge give the same result as the exact one, for the final value of the transition probability.
Radiative mean lives and transition probabilities of electronic states in beam foil excited atomic and ionic carbon
Xenon laser effect on interaction between electron gas and excited atoms in plasma
Atom-atom collisional excitation cross sections obtained from ionization cross sections, noting Thomson classical theory
We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.
Relative rate constants for energy transfer from excited argon atoms to various organic molecules
We study the process of resonant charge exchange involving excited helium atoms with the principal quantum number n = 5 colliding with the helium ion in the ground state in the collision energy range from thermal up to 10 eV. This information may be important for the analysis of planet atmospheres containing helium, in particular, for Jupiter's atmosphere, but our basic interest is the transition from the quantum to classical description of this process, where, due to large cross sections, evaluations of the cross sections are possible. For the chosen process, quantum theory allows determining the cross section as a result of a tunnel electron transition, while classical theory accounts for over-barrier electron transitions. The classical theory additionally requires effective transitions between states with close energies. The analysis of these transitions for helium with n = 5 shows that electron momenta and their projections are mixed for a part of the states, while for other states, the mixing is absent. A simple criterion to separate such states is given. In addition, the main contribution to the cross section of resonant charge exchange follows from tunnel electron transitions. As a result, the quantum theory is better for calculating the cross sections of resonant charge exchange than the classical one and also allows finding the partial cross sections of resonant charge exchange, while the classical approach gives the cross section of resonant charge exchange in a simple manner with the accuracy of 20%.