slide1
Download
Skip this Video
Download Presentation
The H 3 + + H 2 Reaction; A Possible Mechanism for para - H 3 + Enrichment in the Diffuse Interstellar Medium

Loading in 2 Seconds...

play fullscreen
1 / 19

The H3 H2 Reaction; A Possible Mechanism for - PowerPoint PPT Presentation


  • 403 Views
  • Uploaded on

The H 3 + + H 2 Reaction; A Possible Mechanism for para - H 3 + Enrichment in the Diffuse Interstellar Medium. Lieutenant Colonel Brian A. Tom, USAF University of Illinois at Urbana-Champaign Inaugural MWAM, 2008. H 3 + - Abundant and Reactive. (Science, 279 , 1910, 1998) .

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'The H3 H2 Reaction; A Possible Mechanism for ' - salena


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

The H3+ + H2 Reaction; A Possible Mechanism for para- H3+ Enrichment in the Diffuse Interstellar Medium

Lieutenant Colonel Brian A. Tom, USAF

University of Illinois at Urbana-Champaign

Inaugural MWAM, 2008

h 3 abundant and reactive
H3+ - Abundant and Reactive

(Science, 279, 1910, 1998)

(ApJ, 183, L17-20, 1973)

(Nature, 384, 334, 1996)

(ApJ, 185, 505, 1973)

(Phys. Rev., 26, 44, 1925)

h 3 an astrophysical probe
H3+ - An Astrophysical Probe

H2

H3+

Para

Para

Ortho

Ortho

(3:1)

(2:1)

T. Oka, PNAS, 103, 12235, (2006)

para h 3 is enriched in diffuse clouds
Para-H3+ is Enriched in Diffuse Clouds
  • Texcitation measured
  • from H3+ is consistently
  • ~ 40 K lower than H2 –
  • derived Trot ~ 70 K
  • This indicates para-H3+
  • is enriched to ~ 65%

para-H3+

ortho-H3+

Indrioloet al., Ap. J., 671, 1736, (2007)

The cause?

Reaction-induced spin modification

H3+ + H2H2 + H3+

h 3 h 2 h 2 h 3
H3+ + H2H2 + H3+

Identity

+

+

+

+

+

+

Hop

Exchange

M. Cordonnier et al., J. Chem. Phys., 113, 3181, (2000)

h 3 h 2 h 2 h 37

para-H3+ + ortho-H2→ortho-H3+ para-H3+

Hop 2/3 1/3

Exchange 1/3 2/3

para-H3+ + para-H2 → ortho-H3+ para-H3+

Hop 0 1

Exchange 1/3 2/3

H3+ + H2H2 + H3+

ortho-H3+ + ortho-H2

ortho-H2 + ortho-H3+

ortho-H3+ + para-H2

ortho-H2 + para-H3+

para-H3+ + ortho-H2

para-H2 + ortho-H3+

para-H3+ + para-H2

para-H2 + para-H3+

T. Oka, J. Mol. Spec., 228, 635, (2004)

h 3 h 2 h 2 h 38
H3+ + H2H2 + H3+

Problem

ortho-H2

  • Previous model does
  • not account for energy
  • differences between
  • ortho and para ground
  • states

120 cm-1

para-H2

  • Park and Light have
  • addressed this

K. Park and J. Light, J. Chem. Phys., 126, 044305, (2007)

spectroscopy

R(1,0)

R(1,1)u

500

E(cm-1)

J

3

315 cm-1

2

237 cm-1

169 cm-1

87 cm-1

1

64 cm-1

0

0

K

0

1

2

3

(ortho) (para) (para) (ortho)

Spectroscopy
  • Temperature
  • Para-H3+ fraction
spectroscopy11
Spectroscopy

Pulsed Source

Para-H2

generator

Telescope

InSb

LiNbO3

Achromat

Glan Prism

Nd:YAG

AOM

λ/4

λ/2

Wavemeter

Ti:Sapphire

λ/2

an explanation for enrichment
An Explanation for Enrichment?

0.79 ± 0.11

  • Using  = 0.51 ± 0.11, and  = 0.79 ± 0.11;
  • The average para-H3+ fraction measured from 9 diffuse cloud sightlines is 0.65 ± 0.15

Y. Shefferet al., accepted for Astrophys. J. (2008)

conclusions
Conclusions
  • H3+ plays an important role in the interstellar medium
  • We have inferred  = kH/kE = 0.79 ± 0.11 for

60-100 K

    • Could explain para-H3+ enrichment in diffuse ISM
    • More experiments are necessary to understand the underlying process
  • Texcitation by itself is not a reliable measure of rotational temperature in the ISM
slide16

Acknowledgments

  • Andrew Mills, Kyle Crabtree, Michael Wiczer
  • McCall Group
motivation
Motivation

H2+ + H2 → H3+ + H

He

Cosmic Rays

H2+

H+ and H2+

H

H3+

H+

O, C, N, Ne, Mg, Si, Fe…

T. R. Hogness and E. G. Lunn, Phys. Rev., 26, 44, (1925)

T. Oka, PNAS, 103, 12235, (2006)

ad