Interstellar H3+ in Metastable Rotational Levels

Takeshi Oka and Erik Epp

Department of Chemistry and Department of Astronomy and Astrophysics,

The Enrico Fermi Institute, The University of Chicago

the 58th International Symposium on Molecular Spectroscopy

Columbus Ohio, FA06,10:27, June 20, 2003

Δk = 3 Forbidden Rotational Transitions in H3+

Interstellar NH3 Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971)

General Theory Watson, J. Mol. Spectrosc. 40, 536 (1971)

H3+ Pan, Oka, ApJ 305, 518 (1986)

Ab initio H3+ Neale, Miller, Tennyson, ApJ 335, 486 (1988)

μ

Δk = 3 Forbidden Rotational Transitions in H3+

Interstellar NH3 Oka, Shimizu, Shimizu, Watson, ApJ 165, L15 (1971)

Theory Watson, J. Mol. Spectrosc. 40, 536 (1971)

H3+ Pan, Oka, ApJ 305, 518 (1986)

Theory H3+ Neale, Miller, Tennyson, ApJ 335, 486 (1988)

Metastable

27.2 days

20.4 days

15.8 hours7.9 hours

3.8 hours

32

3

4

3ji jiAc

μ

Quasi-metastable

11.4 years

4000 cm-1

2000 cm-1

0

Radiation Collision Reaction

Rigorous Selection Rules Approximate Random

ortho para ΔI = 0 ortho para ΔI = 0 ΔItotal = 0 + - ΔJ = ± 1, 0

A

A

B

B

C

A

D

B

Rate Equations

1' ' ' '2

' '

( ) exp( )2

J K JK JK J KJK JK

J K

g E Ek C

g kT

2

' '' '

' '

' '' '

' '

( )( ) ( )

( ' ') ( )

( ' ') ( )

( ) ( ) ( ) ( )

J K JKJK J K

J K

J K JKJK J K

J K

e XX

dn JKn H f JK

dt

A n J K A n JK

k n J K k n JK

k n e n JK k n X n JK

2( )JK LJK

C k n H

Production

Spontaneous emission 4 10-7 s-

1

Collision n(H2) 100 cm-3 10-7 s-1

Destruction 10-9 s-1

10-17 s-1

10-7 cm3 s-1 10-9 cm3 s-1

' '' '

' ' ' '

exp( )J KJK JK JK J KJKJ K J K

k g E E

k g kT

H3+ + H2 (H5

+)* H3+ + H2

Detailed balance

12345

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4N

orm

aliz

ed P

op

ula

tio

n

n(H2)

Level

Normalized Populations of H3+ Rotational Energy Levels

T 1000 (K), n(e-) 1E-06 (cm-3), n(X) 0.0001 (cm-3)

0.11101001000

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5N

orm

aliz

ed P

op

ula

tio

n

n(H2)

Level

Normalized Populations of H3+ Rotational Energy Levels

T 300 (K), n(e-) 1E-06 (cm-3), n(X) 0.0001 (cm-3)

Normalized Populations of H3+ Rotational Energy Levels for Various H2 densities

T 1000 (K), n(e-) 1E-06 (cm-3), n(X) 0.0001 (cm-3)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Level

Norm

aliz

ed P

opul

atio

n

0.1

1

10

100

1000

Normalized Populations of H3+ Rotational Energy Levels for Various H2 densities

T 300 (K), n(e-) 1E-06 (cm-3), n(X) 0.0001 (cm-3)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Level

No

rmal

ized

Po

pu

lati

on

0.1

1

10

100

1000

Ortho-H3+

Para-H3+

Para-H3+

Para-H3+

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 200 400 600 800 1000 1200

Tsim

Te

x/T

sim

n(H2)1000

n(H2)100

n(H2)10

n(H2)1