Levels Of Atomic Hydrogen Research Articles

Eikonal Theory of Inelastic Electron-Atom Scattering at Intermediate Energies

An eikonal distorted-wave theory is proposed for inelastic electron-atom collisions at intermediate energies. The primary interaction, responsible for the transition, is treated to first order, while the initial- and final-state interactions are taken into account by using the eikonal approximation. Direct and exchange collisions are both considered. Detailed numerical calculations are performed for the excitation of the n=2 levels of atomic hydrogen by electron impact. The results for the differential excitation cross sections are compared with those obtained in the Glauber eikonal approximation at small scattering angles. © 1972 The American Physical Society.

Glauber Amplitudes in Charged Particle Hydrogen Atom Collisions

The Glauber scattering amplitudes for the excitation of the ns and np levels of atomic hydrogen by electrons (or protons) incident upon the ground state have been obtained in closed form. In contradistinction to previously quoted results, these new expressions require no numerical integration. For small n, the amplitudes reduce to simple sums of hypergeometric functions. Hence the Glauber amplitudes for these transitions now can be computed with scarcely more difficulty than the Born amplitudes. A selection rule for arbitrary transitions is derived.

Exact Treatment of the Stark Effect in Atomic Hydrogen

A boundary-condition method is used to investigate the energy levels of atomic hydrogen in a uniform electric field. At low fields the misbehavior of trial eigensolutions in the nonclassical region enables one to obtain high-accuracy upper and lower bounds to the Stark shift. At higher fields the energy levels are treated as resonant states imbedded in a continuum. A modified WKB approach is used to obtain both the position and width of these resonances. Comparison is made with the usual perturbation-theory results.

Classical cross sections for the electron ionization of the degenerate levels of the excited states of atomic hydrogen

The classical theory of Gryzinski is used to obtain cross sections for the electron ionization of the degenerate levels of atomic hydrogen. The results are compared with the Born approximation cross sections and it is found that the agreement is good. As the principal quantum number is increased the classical and quantal cross sections tend to one another at all values of the incident electron energy for all azimuthal quantum numbers.

Oscillator Strengths for High-level Transitions in Hydrogen

TRANSITIONS between high quantum levels of atomic hydrogen can produce spectral lines in the radio region. Observers have detected a number of such emissions from hydrogen gas in various radio sources. Theoretical interpretation of such observations requires knowledge of the oscillator strengths fn+c,n for transitions described by the quantum transition n+c→n. For n large and c small, the fs follow the asymptotic formula with Jc(c) is the Bessel function of equal order and argument and J′c(c) is the first derivative with respect to the argument. Table 1 contains a few representative values of M(c).

Departures from LTE in g- and k- Star Atmospheres

A series of non-LTE model atmospheres in the range 40000 < Teff < 60000 K with log g = 2 and 4.44 has been computed. In the calculation of these models, the equations of statistical equilibrium for H- and the first three levels of atomic hydrogen and the equations of radiative transfer and hydrostatic equilibrium have been solved simultaneously. The computed temperature-pressure relationships and the emergent fluxes are found to be sensitive to the choice of the reaction rate C__ for associative detachment of H-. The effects of the computed departures from LTE on solar limb darkening and stellar fluxes suggest several observational tests for detecting the departures. One of these tests, for which the requisite data are available, indicates that the atmospheres of late G and early K giants may be affected significantly by deviations from LTE.

Low-energy electron scattering by atomic hydrogen: I. The close-coupling approximation

The results of a six-state close-coupling calculation of low-energy electron scattering by atomic hydrogen are presented. The first six hydrogen atom eigenstates are retained in the expansion of the total wave function and the resultant equations solved on a C.D.C. 6600 computer. Resonances are found below the n = 3 excitation threshold of atomic hydrogen and they are shown to play an important role in the excitation cross sections Q(1s-2s) and Q(1s-2p). For energies insufficient to excite these resonances it is found that the three-state close-coupling approximation gives reliable results. Finally, cross sections are given for the transitions between the n = 1 and 3 and the n = 2 and 3 levels of atomic hydrogen as well as for elastic scattering on the ground state.

The Populations of the Discrete Levels of Atomic Hydrogen in the Chromosphere.

view Abstract Citations (2) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Populations of the Discrete Levels of Atomic Hydrogen in the Chromosphere. Kingston, A. E. Abstract We consider the effect of electron collision processes on the populations of the discrete levels of atomic hydrogen in the chromosphere. The rate coefficients for collisional processes are much larger than those used in previous calculations. It is found that the difference in the populations of all the excited states from the thermodynamical equilibrium values is considerably changed from the results obtained in previous calculations. For states with principal quantum number, j> 10, the populations are close to what we would obtain if we assumed local thermodynamical equilibrium conditions. Publication: The Astrophysical Journal Pub Date: August 1964 DOI: 10.1086/147967 Bibcode: 1964ApJ...140..736K full text sources ADS |

Spectroscopic Study of Controlled Proton Impact on Molecular Nitrogen

Protons of energy 5-130 keV were passed into molecular nitrogen gas at low pressure and the resulting radiation spectroscopically analyzed. Prominent emissions studied were: (1) two ${\mathrm{N}}_{\mathrm{II}}$ lines located at $\ensuremath{\lambda}5005$ \AA{} and $\ensuremath{\lambda}5680$ \AA{}; (2) bands of the ${\mathrm{N}}_{2}^{+}$ first negative band system ($B^{2}\ensuremath{\Sigma}\ensuremath{-}X^{2}\ensuremath{\Sigma}$); and (3) two Balmer lines, ${H}_{\ensuremath{\alpha}}$ and ${H}_{\ensuremath{\beta}}$, formed by charge changing collisions with nitrogen molecules. Absolute cross sections for the production of these emissions were measured as a function of the energy of the incident protons. Population cross sections for the $v=0$ and $v=1$ levels of the $B^{2}\ensuremath{\Sigma}$ state of ${\mathrm{N}}_{2}^{+}$ were obtained as well as an estimate of the level population cross section of the $n=3$ and $n=4$ levels of atomic hydrogen formed by charge exchange.

The Excitation of the Discrete Levels of Atomic Hydrogen by Fast Electrons

The cross sections for the excitation of normal hydrogen atoms to the fifth and higher levels have been obtained by interpolation from the Born cross sections for the excitation to the second, third and fourth levels, and for ejection into the continuum. The cross section describing the excitation of all levels and the energy loss sustained by the incident electron are hence derived.