On Strong Collisions in Hydrogenic Line Broadening

Abstract

The degeneracy of hydrogenic states is used to sum approximately the 5-matrix to all orders in Starkbroadening calculations. It is found that the usual strong-collision cutoff for lower lines should represent a reasonable approximation. However, there could be a significant difference between our results and previous calculations for transitions among levels with large principal quantum numbers.

The Effect of time ordering on the Lyman α profile

“…In the results of Bacon, Shen, and Cooper [6] the final profiles were normalized to one in the line center. A plot of the data from this calculation yields an increase in the half-width of the line due to time ordering by about 14 percent (this is in close agreement with the results of the Bacon, Shen, and Cooper calculation versus that for the Shen-Cooper case [3]).…”

“…The half-width increases over the un-time-ordcred resuh by about 14 percent. This is in agreement with a comparison of the impact calculation [6] and the results of Shen and Cooper [3]. As one goes towards the wings of the profile the effect of timeordering eventually causes an increase in the intensity of the profile.…”

“…Initially, the calculations of the S-operator were made to second order only. Later Shen and Cooper [3] were able to calculate the un-time ordered 5-operator to all orders. In the other limit, quasi-static theories were used to describe the wings of the profile (Aai-?…”

“…Further, as in the case of Shen and Cooper [3], the calculations were made to all orders for the un-time-ordered exponential form of the time-development operator. The interaction potential was approximated to be of the dipole type and the ion broadening was treated as quasi-static. The correlation between the plasma perturbers was considered by cutting off the interaction potential at the Debye-length of the plasma.…”

Committee 3: Collision Cross Sections and Line Broadening

“…The theory of Stark broadening of hydrogen lines has been improved (15,21) and extended to lower densities and higher quantum numbers (17), and semi-empirical formulae have been given for line wings (18). The Lya line has been studied, with special emphasis on the contribution from strong impacts (19,20). Further calculations have been made for Hei lines, with forbidden components, using a theory similar to that used for Hi (22,23,24).…”