OH (1720 MHz) masers serve as indicators of SNR - molecular cloud interaction sites. These masers are collisionally excited in warm (50-100 K) shocked gas with densities of order 105cm3 when the OH column density is in the range 10161017cm2. Here I present excitation calculations which show that when the OH column density exceeds 1017cm2 at similar densities and temperatures, the inversion of the 1720 MHz line switches off and instead the 6049 MHz transition in the first excited rotational state of OH becomes inverted. This line may serve as a complementary signal of warm, shocked gas when the OH column density is large.
|Number of pages||2|
|Journal||Proceedings of the International Astronomical Union|
|Publication status||Published - Mar 2007|
- Molecular processes
- Radiation mechanisms: nonthermal
- Radio lines: ISM
- Supernova remnants