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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 h 3 a closer look

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 ….


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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?


Storage ring measurements of the dissociative recombination of h 3 a closer look

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)


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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+


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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)


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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)


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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?


Storage ring measurements of the dissociative recombination of h 3 a closer look

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+


Storage ring measurements of the dissociative recombination of h 3 a closer look

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?


Storage ring measurements of the dissociative recombination of h 3 a closer look

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


Storage ring measurements of the dissociative recombination of h 3 a closer look

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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