The Non-Thermal Rotational

Distribution of Interstellar H3+

(ApJ, in press )

Takeshi Oka and Erik Epp,

Department of Astronomy and Astrophysics,

and Department of Chemistry,

The Enrico Fermi Institute,

The University of Chicago

59th Ohio State University In ternational Symposium on Molecular Spectroscopy, RI 05, 2:51 pm, June 24, 2004

8

6

4

2

0

N(H

3+)

in 1

01

4 cm

-2

16012080400Av

151050Av

8

6

4

2

0

Dense Clouds Diffuse Clouds

Diffuse CloudsGC

Dense cloudsMcCall, Geballe, HinkleOka, ApJ 522,338(1999)

Diffuse cloudsMcCall, Hinkle, Geballe, Moriarty-Schieven, Evans, Kawaguchi, Takano, Smith, Oka, ApJ 567, 391 (2002)

W33A

AFGL2136

AFGL 2591

AFGL 490

AFGL 961EMonR2 IRS3

Cygnus OB2 #12

WR 118

# 5WR 104

WR 121

HD 20041

183143

Ζ Per

Ubiquitous H3+

Dense Clouds

Diffuse Clouds

GC

Galactic plane

Quintuplet

H3+ toward the Galactic center

N(H3+) = 17.5(3.9) × 1014 cm-2 GC IRS 3

27.7(2.4) 1014 cm-2 GCS 3-2

Geballe, McCall, Hinkle, Oka, ApJ 510, 251 (1999)

GC IRS 3

Δk = 3 Forbidden Rotational Transitions in H3+

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

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

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

Metastable

27.2 days

20.4 days

μ

Critical Density

200 cm-3

R(3, 3)l

R(2, 2)l

(3, 3)

(2, 2)

Very Non-thermal

Radiation Collision Reaction

Rigorous Selection Rules Approximate Rules Random

+ - ΔJ = ± 1, 0

ortho para ΔI = 0 ortho para ΔI = 0 ΔItotal = 0

A

A

B

B

C

A

D

B

Ψ’

ψ

Trad 3 K « Tkin

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

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

Cosmic ray ionization

Dissociative recombination Proton hop reaction

0 =

Steady State

n(3,3)/n(1,1)

n(3,3)/n(2,2)

Tex from n(1,0)/n(1,1)

Ortho-H3+

Para-H3+

Para-H3+

Para-H3+

T(H2) = 10 K

T(H2) = 60 K

032.86 K

151.33 K

249.26 K

Gemini South

Quasi-metastable

11.4 years

Summary

Metastable level (3, 3) populated

Unstable levels (2, 2) and (2, 1) unpopulated

Spontaneous emission, chemical collision

High Temperature (T> 200 K)

Low density (n< 100 cm-3)

Other metastable levels (4, 4), (5, 5), (6, 6)

More observations of unstable levels