Coherence parameters of atomic excited states: comparison of results from the CTMC and the quantal calculations

Cross sections for electron capture in collisions between H + and laser-excited oriented Na(3p −1 ) atoms have been computed at intermediate energies (5-50 keV). A quantal method is used within the atomic orbital close-coupling approach as well as a purely classical model, i.e. the classical trajectory Monte Carlo method. Both methods are in good agreement over the entire energy range for total capture cross sections and partial n = 2 cross sections. At the level of state-to-state differential cross sections some differences between the two approaches become evident. The total probability for electron transfer in both methods turns out, however, always to be largest in left-hand side collisions where the projectile velocity can become parallel to (match) the electron velocity of the Na(3p −1 ) target.

Section: Introductionmentioning

confidence: 99%

Orientation effects for collisions at energies beyond the `velocity-matching' region

Hansen

Nielsen

et al. 1998

“…In a recent paper, Toshima and Lin (1991) examined the coherence parameters of excited states formed in collisions of hydrogen atoms with electrons, positrons, protons and antiprotons using the classical trajectory Monte Carlo (CTMC) method and compared the results with those obtained from quantal calculations. The excited states examined were the n = 2 states formed by electron capture or by excitation processes.…”

mentioning

confidence: 99%

“…One more ambiguity about the CTMC is the choice of ensemble average for the initial state. In the previous study (Toshima and Lin 1991) only the microcanonical ensemble was considered since excitation processes were examined there and it is desirable to have a well defined energy for the initial state. In the present paper, we consider the electron capture channels only.…”

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confidence: 99%

Orientation parameters and dipole moments of He⁺(n=2) states in He²⁺+H collisions: comparison of CTMC and close-coupling results

Toshima

Shingal

Lin

1992

The orientation parameter and the dipole moment of the n=2 states of He+ resulting from electron capture in He2++H collisions are examined using the classical trajectory Monte Carlo (CTMC) method and the close-coupling expansion using two-centre atomic orbitals at 10, 25 and 50 keV amu-1. It is shown that the orientation parameters calculated from the two theories are in good agreement but large discrepancies exist for the dipole moments. Together with previous similar comparisons for p-H collisions, the authors conclude that the CTMC method is not reliable in predicting the coherence parameters of excited states formed in atomic collisions.

“…Capture predictions for the n = 3 and 4 channels from classical and quantum methods, however, are in better agreement concerning magnitudes and scattering range. We do note, however, that the detailed assignment of a final n-level in CTMC is not unique and other boundary procedures than ours [9] could redistribute the level probabilities somewhat.…”

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confidence: 68%

Left/right capture asymmetry in He²⁺-Na(3p_-1) collisions: classical versus quantal collision dynamics

Dubois¹,

Nielsen²,

Hansen³

et al. 2000

Differential collision results based on classical (CTMC) and quantal (AOCC) calculations for single-electron capture in collisions of He 2+ projectiles with oriented Na(3p −1 ) atoms are compared at three intermediate impact energies (velocities of 0.45, 0.86 and 1.21 au). Good agreement between the two methods is reported with respect to the total capture probability, differential cross section and left/right scattering asymmetry. The polarization interaction with the target is so strong that the repulsive scattering in the final capture channels is seen only at the highest energy as a direct correspondence of left-/right-hand side trajectory results and left-/right-hand side scattering results. State-to-level and state-to-state capture results reveal differences between the predictions of classical and quantal methods.