A Study of Van Der Waals Broadening for Lines of Astrophysical Interest.
Abstract
When the perturber is atomic hydrogen the Van Der Waals interaction constant C6 can be determined exactly for both the ground and excited states of the perturbed atom. A computational method was developed which allows the calculations to be carried out in a systematic and time saving manner. Using this method, interaction constants were computed for 14 energy levels of Na I which gave rise to all of the Na I lines in the visible region of the solar spectrum, as well as the levels of some selected Mg I and Ca II lines. The results were compared to those obtained using the most commonly employed Coulomb-approximation methods. Both methods gave nearly identical results for highly excited states, but for the lowest levels, the exact method yields answers which were systematically smaller, amounting to a maximum difference of 20% for the ground state of Na I. A further comparison of C6 for the ground state of Na I to the value derived by Dalgarno using his One-Center method, the only other exact method known, shows excellent agreement.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1976
- Bibcode:
- 1976PhDT.........5M
- Keywords:
-
- Physics: Astronomy and Astrophysics;
- Astrophysics;
- Atomic Excitations;
- Monatomic Gases;
- Van Der Waals Forces;
- Hydrogen;
- Sodium;
- Solar Physics;
- Solar Spectra;
- Astrophysics