Lecture 8 - Ionisation and Recombination

Question 1

What’s a dissociative recombination?

Answer 1

AB^+ + e^- –> A + B + delta E

Question 2

Is charge exchange a type of ionisation and recombination?

Answer 2

Yes

Question 3

Generally, are both objects involved in a charge exchange electrically charged?

Answer 3

No, one must be neutral atom.

Question 4

When do charge exchange reactions occur rapidly?

Answer 4

When there is “level crossing” that is energetically attainable

Question 5

What characterizes a cosmic ray ionisation?

Answer 5

One particle being a relativistic nucleus (H+, He++, Fe26+)

Question 6

Where are cosmic ray ionisation important?

Answer 6

In the centers of molecular clouds and near the galactic center region

Question 7

What type of gas do Strömgren spheres describe?

Answer 7

HII gas

Question 8

Normal size of a Strömgren sphere is…

Answer 8

about 30 kpc in radius

Question 9

Criterion for a compact Strömgren sphere

Answer 9

R_s < 1 pc

Question 10

Criterion for a ultra-compact Strömgren sphere

Answer 10

R_s < 0.1 pc

Question 11

Criterion for a hyper-compact Strömgren sphere

Answer 11

R_s < 0.01 pc