Engineering topics
Publications and source records attributed to Drachman, R. J..
Using the precision s- and p-wave elastic-scattering wave functions obtained previously, we have calculated the annihilation rate for positrons colliding with hydrogen atoms below the positronium-formation threshold. The s-wave results agree well with those of Humberston, while the p-wave results, which are new, contribute about 20% of the total at the higher energies.
It is shown that difficulties in atomic scattering calculations that stem from the use of inexact target wave functions can be overcome by employing the so-called method of models, provided that the projectile is distinguishable from the atomic electrons. The proposed method of models consists in replacing the target hamiltonian by a model hamiltonian, of which the appropriate target state is an eigenfunction. A connection with the positron scattering work of Peterkop and Rabik (1971) has been established.
An error in a previous modified adiabatic approximation (Drachman, 1966), due to a lack of generality in the form of the short-range correlation part of the wave function for L greater than zero, is corrected heuristically by allowing the monopole suppression parameter to depend on L. An L-dependent local potential is constructed to fit the well-known positron-hydrogen s, p, and d wave phase shifts below the rearrangement threshold. The same form of potential yields a positron-helium cross-section in agreement with a recent experimental measurement near threshold.
Positron-hydrogen scattering below positronium pickup threshold by Hylleraas bound technique, discussing phase shifts and linear parameters
S wave scattering from H and He positron systems at low energies, applying Kohn and Harris variational methods
Simplified model for positronium-helium scattering
Positron annihilation in helium
Adiabatic correlation function for variational lower bounds on positron-atom elastic scattering phase shifts for hydrogen and helium atoms
Positron-H scattering, discussing possible scattering resonance below positronium thresholds
First order adiabatic correlation function for determining variational bounds in positron-atom scattering
Isospin impurity mixing in distorted deuteron reaction
Modified adiabatic scattering function applied to positron annihilation in helium
Modified adiabatic scattering function applied to positron annihilation in helium
Positron-helium scattering below positronium threshold, using adiabatic method previously tested in positron hydrogen scattering, presenting phase shifts and momentum transfer cross section computations
Theory of low energy positron helium scattering below positronium threshold - adiabatic method applied
Positron s-wave elastic scattering by atomic hydrogen below inelastic threshold analyzed, using Dalgarno-Lynn second order adiabatic potential