Molecule formation and infrared emission in fast interstellar shocks. II. Dissociation speeds for interstellar shock waves

Journal Article · Wed Oct 01 04:00:00 EDT 1980 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/183358· OSTI ID:6678023

Hollenbach, D; McKee, C F

The postshock destruction of molecules is examined, including the processes of (i) collisions with neutral hydrogen atoms and molecules, (ii) electronic collisions, and (iii) neutral chemical reactions with atoms, particularly atomic hydrogen. Using conservative estimates of collisional dissociation rates from individual vibrational states, we find that process (i) leads to the destruction of molecular hydrogen behind shocks with speeds v/sub s/> or approx. =25 km s/sup -1/ if the preshock molecular gas has hydrogen nucleus densities of n/sub 0/> or approx. =10/sup 4/ cm/sup -3/. At lower densities (n/sub 0/approx. =10/sup 2/ cm/sup -3/), destruction occurs for v/sub s/> or approx. =50 km s/sup -1/ and process (ii) dominates. Dissociation of molecules such as CO, H/sub 2/O, and O/sub 2/ follows the destruction of H/sub 2/, as the resultant hydrogen atoms chemically dissociate the metal atoms from their bonds (process iii) in the hot postshock gas. These results demonstrate that many of the observed high-speed interstellar molecules, if shock accelerated, must have dissociated and reformed in the postshock gas.

• Research Organization: Space Science Division, NASA Ames Research Center, Moffett Field, California
• OSTI ID: 6678023
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Journal Name: Astrophys. J., Lett. Ed.; (United States) Vol. 241:1; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
COLLISIONS
DISSOCIATION
ELECTROMAGNETIC RADIATION
INFRARED RADIATION
INTERSTELLAR GRAINS
INTERSTELLAR SPACE
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
MOLECULES
PARTICLES
RADIATIONS
SHOCK WAVES
SPACE