الفهرس Only 14 pages are availabe for public view
 |  | from | 135 |  |  |
| | | from | 135 | | |
Abstract
The observed high abundances of gaseous formaldehyde (H2CO) and methanol (CH30H) in interstellar, circumstellar, protoplanetary mediums and cometary regions indicates that they could not be produced only via gas-phase reaction routes, but there must be other routes to produce them such as surface reactions. Recent observations from the European Infrared Space Observatory (ISO) and others, confirmed the presence of a number of solidified species in the interstellar medium including H2CO (3.475µm) and CH30H (3.54, 3.9, and 9.75µm). In order to explain. such observations, many experimental as well as theoretical works have been done. Tielens and Hagen (1982) calculated numerically the chemical compositions of mantles accreting on grains with a chemical reaction scheme which comprises gas-phase as well as grain surface reactions. Although the formation of H2CO in their scheme on grain surfaces was via the successive hydrogenation of CO molecules, they did not include the formation of CH30H via this process in their model (see Figure 5 in ,their paper). In 1992, Hasegawa et al. built models of gas-grain chemistry in dense clouds which include complex organic molecules such as H2CO, CH30H, H3CgN, and others. The successive hydrogenation of CO on grain surfaces led to the formation of H2CO while the hydrogenation of H2CO itself led to its destruction into HCO and H2 rather .