Year: 1993
Type: article
Abstract: A theory is presented in which the carriers of the diffuse interstellar bands are members of an unspecified class of molecular hydrides denoted XHm, (m = 0, 1, ... , mmax). The bands are carried by several different species which differ in m, the number of hydrogen atoms they bear. This difference between carriers has observable consequences because the average number of hydrogen atoms per molecule in the interstellar population is taken to be variable from place to place and to be determined by a dynamical equilibrium between photodetachment and chemical attachment reactions. Carriers with different numbers of hydrogen atoms are expected to have different interstellar habitats, and it is suggested that this underlies the observational partitioning of the bands into families. The carriers are assumed to be well mixed with the interstellar gas and dust, but even so the equivalent width Wλ. of any band is not simply proportional to the reddening E(B – V); it also depends on what fraction of the population along the line of sight is in the form of the appropriate carrier. This fraction is an independent variable whose behaviour is expected to leave distinctive effects on plots of Wλ. against E(B – V), and these effects are sought in measurements of λλ5797 and 5780 Å. It is found that the fractional abundance of both carriers is low in dense gas and that there are differences between the plots which indicate that the carrier of λ5780 bears more hydrogen atoms than that of λ5797. Reasons are given for considering the fulleranes C60Hm as the carriers.
Author: A. Webster
Institution: Royal Observatory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2102744475