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Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look PowerPoint PPT Presentation


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Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look. Holger Kreckel University of Illinois at Urbana-Champaign. … studied in the laboratory. A fundamental process in space …. MWAM 2010, Nov 6th 2010 Holger Kreckel. Neutral fragments. Molecular ion.

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Storage ring measurements of the Dissociative Recombination of H 3 + : a closer look

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Storage ring measurements of the

Dissociative Recombination of H3+: a closer look

Holger Kreckel

University of Illinois at Urbana-Champaign

… studied in the laboratory.

A fundamental process in space ….


MWAM 2010, Nov6th 2010

Holger Kreckel

Neutral fragments

Molecular ion

Free electron

Storage ring measurements … of H3+: a closer look

Dissociative recombination of molecular ions

AB+ + e- A + B


MWAM 2010, Nov6th 2010

Holger Kreckel

O2+ + e-→ O* + O

O (1S → 1D) emission at 5577 Å

1st step: DR of O2+

2nd step: emission from excited atomic products

Storage ring measurements … of H3+: a closer look

Brief History of Dissociative Recombination (DR)

Solar radiation produces a lot of electrons in the Ionosphere by photoionization.

How are these electrons removed?


MWAM 2010, Nov6th 2010

Holger Kreckel

Direct DR process

Storage ring measurements … of H3+: a closer look

Dissociative recombination of molecular ions

Bates, D.R., “Dissociative Recombination”, Phys. Rev. 78, 492 (1950)


MWAM 2010, Nov6th 2010

Holger Kreckel

H2 + H

H2

e-

H3+ formation

and destruction

cosmic ray

H2 H2+ H3+

H + H + H

OH + H2

H2

H3+

H2

e-

Water formation

OH3+

OH+

OH2+

O

H2O + H

H2

OH

e-

HCO+

CO+

C+

H + CO

Carbon chemistry

Storage ring measurements … of H3+: a closer look

Importance of DR in the interstellar medium


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

The Problem with H3+ DR (experiment)

H2+H

H+H+H

H3++e-

DR rate coefficient

upper limits


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

The Problem with H3+ DR (experiment)

H2+H

H+H+H

H3++e-

DR rate coefficient

upper limits


MWAM 2010, Nov6th 2010

Holger Kreckel

• Vibrations cool

• Rotations stay forever

Kreckel et al., PRA A 66, 052509 (2002),

Kreckel et al., New J. Phys. 6, 151 (2004)

Storage ring measurements … of H3+: a closer look

Storage ring measurements: concept

Advantages

•radiative relaxation

of internal excitations

(rotation, vibration)

  • direct measurement

  • 100% detection efficiency

  • high resolution

Problem

H3+


MWAM 2010, Nov6th 2010

Holger Kreckel

5 cm

Pinhole flange/ground electrode

-900 V

ring

electrode

TSR

2004

Cryogenic

ion trap

H3+

Storage ring measurements … of H3+: a closer look

Rotationally “cold” ion sources

Gas inlet

2 atm

H2

Solenoid valve

CRYRING

2002

Supersonic

expansion


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Storage ring results with “cold” H3+ ion sources

● TSR electron temp.

kT┴=0.5 meV ~ 6K

kT||=25 μeV

trap temp. 13 K

Kreckel, PRL 95, 263201 (2005)

●CRYRING

kT┴=2 meV

ion temp. 30-50 K

McCall, Nature

422, 500 (2003)

Theory

Kokoouline

and Greene


MWAM 2010, Nov6th 2010

Holger Kreckel

+

+

Storage ring measurements … of H3+: a closer look

The holy grail: state specific measurements

para

I = 1/2

ortho

I = 3/2

H3+

rotational

levels


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Nuclear spin effect: exp. and theory 2005

۰para H2

۰normal H2

experiment

kT┴=4 meV

theory

Greene et al.

- para

- ortho

Kreckel et. al, PRL 95, 263201 (2005)


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Theory with more accurate resonance energies

S. Fonseca dos Santos et al., JCP 127, 124309 2007


MWAM 2010, Nov6th 2010

Holger Kreckel

plunger

locking nut

discharge

electrode

skimmer

high pressure

H2 reservoir

low pressure

pinhole

6 cm

piezo actuator

Storage ring measurements … of H3+: a closer look

Piezo expansion source


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Rotational temperature of H3+ inferred from

cavity ring-down spectroscopy of the ion source

pure H2 discharge, 2bar

Trot=110 K

1:5 H2:Argon discharge, 2bar

Trot=180 K


MWAM 2010, Nov6th 2010

Holger Kreckel

para H3+

para H3+

ortho H3+

p-H3+ fraction p3= (47.9 ± 2) %

1:5 n-H2 : Argon mixture

p-H3+ fraction p3= (70.8 ± 2) %

1:5 p-H2 : Argon mixture

Storage ring measurements … of H3+: a closer look

Nuclear spin manipulation


DR 2010, Lake Tahoe, Aug19th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

DR measurements at TSR

UI Champaign-Urbana

MPI-K Heidelberg

Test Storage Ring


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Comparison to CRYRING 2002

TSR 2009 (n-H2:Ar 1:5)

CRYRING 2002 (n-H2)


MWAM 2010, Nov6th 2010

Holger Kreckel

ne(cooler) = 1.4 x 107 cm-3

ne(target) = 1.34 x 106 cm-3

Storage ring measurements … of H3+: a closer look

2-dimensional imaging of the 3-body breakup

H3+ + e- H + H + H


MWAM 2010, Nov6th 2010

Holger Kreckel

rotational

temperatures

(uncertainties ~ 200 K)

950 K

450 K

200 K

Storage ring measurements … of H3+: a closer look

2-dimensional imaging of the 3-body breakup

H3+ + e- H + H + H


MWAM 2010, Nov6th 2010

Holger Kreckel

skimmer

Storage ring measurements … of H3+: a closer look

Conditions on-axis downstream of the nozzle

Collisional

heating during

Ion extraction?


MWAM 2010, Nov6th 2010

Holger Kreckel

Reduced

rate coeff.

Storage ring measurements … of H3+: a closer look

Nuclear spin dependence of the rate coefficient

p3= (47.9 ± 2) %

1:5 n-H2 : Argon mixture

p3= (70.8 ± 2) %

1:5 p-H2 : Argon mixture

Extrapolation:

100% ortho H3+

100% para H3+


MWAM 2010, Nov6th 2010

Holger Kreckel

Still out there …

Storage ring measurements … of H3+: a closer look

Summary

• While we measure a rotational temperature of 200K with CRD spectroscopy,

the stored H3+ ions are much hotter than the ion source.

• We observed clear differences between different ion sources

→ the heating is probably happeningprior to injection into the ring.

• We observed for the first time detailed structures in

the rate coefficients for ortho-H3+ and para-H3+ at low energies.

Results: Kreckel et al., 82, 042715 (2010)

Petrignani et al., in preparation

The holy grail?


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Collaboration

TSR

Group

University

of Illinois

Kyle N. Crabtree

Brian A. Tom

Benjamin J. McCall

Oldřich Novotny*

Annemieke Petrignani

Max H. Berg

Dennis Bing

Manfred Grieser

Claude Krantz

Michael Lestinsky*

Mario B. Mendes

Christian Nordhorn

Roland Repnow

Julia Stützel

Andreas Wolf

Weizmann

Institute

Henrik Buhr

Stockholm

University

Richard Thomas

*Columbia University, NY

German-Israeli

Foundation

National

Science

Foundation

Max-Planck

Society

Funding:

Eurppean

Comission


MWAM 2010, Nov6th 2010

Holger Kreckel

Storage ring measurements … of H3+: a closer look

Perspectives:

the case to continue the quest

It is crucial to understand:

H3+ + H2 and

H3+ (J=1,K=0,1) + e-

Next speaker: Kyle Crabtree


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