Progress in measurements of dissociative recombination CRP on Atomic and Molecular Data for Plasma Modelling Mats Larsson Department of Physics Stockholm.

Progress in measurements of Progress in measurements of dissociative recombinationdissociative recombination CRP on Atomic and Molecular Data for Plasma ModellingCRP on Atomic and Molecular Data for Plasma Modelling

Mats Larsson

Department of Physics

Stockholm University

Task for Stockholm according Task for Stockholm according to minutes of 2005to minutes of 2005

BeH+ and BeH2+

Problem: The Manne Siegbahn Laboratory reluctant to deal with Be.

Some pointsSome points

The Stockholm group has no national funding for fusion related research

The storage ring CRYRING is still in operation and beam time will be scheduled for the fall of 2007. The decision to shut down the lab was taken 2002, so the damage control has been quite successful!

Beam time during 2008 unclear

ProgressProgress

Experiment on C4D2+

Results on CF2+ and CF3

+

The H3+ and its isotopologues

Development of data base for dissociative recombination

Doubly excited neutral molecule

A2+B

AB+A

A+A+B

+

e-

DR of polyatomic ions

A2B+ + e- (Ee)

For example:

C2H+ + e- C2 + H + 6.60 eV

CH + C + 3.98 eV

C + C + H + 0.43 eV

3 possible DR -

channels

Research programme

What do we measure?:

• Branching fractions of dissociative recombination• Thermal rate constants/Cross sections of dissociative recombination (energy/temperature – dependence)

Which ions do we study?:

- hydrocarbon ions (so far C2H+, C2H2+, C2H3

+, C2H4+, C2D5

+

C3H4+, C3H7

+, C4D9+, C4D2+), CFn+, H3

+

Manne Siegbahn Laboratory

52 meters circumference

ExperimentExperiment

• Long storage time – internal relaxation

• Multi-pass experiment

CRYRING Heavy Ion Storage Ring

electrons

neutrals

ions

Interaction - DR

ions

dipole magnet

SBD

• Electron cooling – well defined beam size

• Ions interact with electrons – dissociative recombination

• Well defined collision energies - velocity matched conditions

• Detect neutral fragments (from DR process)

A2+ + e A + A; no grid

2A

Energy

Pulse height spectrum

A2+ + e A + A; grid with 30% transmission

2A

A

Energy

All fragment from one DR event hit the detector at the same time yield a pulse at an energy corresponding to full beam energy

Gives no information about

how the molecule breaks up

DR Branching DR Branching fractionfraction measurement measurement

C2H++e-

Relate the fragments to different dissociation channels!

C2H++e-

2C

C+H

C

2C+H

DR Branching DR Branching ratioratio measurement measurement

C2H+ + e- C2

+ H

CH + C

C + C + H

e-

γN

βN

αN

T)-2T(1T)-T(10

T)(12TT)-T(10

T)-(1T0T)T(1

TTT

CN

HCN

2CN

H2CN

2

2

2

322

DR Branching DR Branching ratiosratios – Hydrocarbon – Hydrocarbon ionsions

Products Ratio Products Ratio Products Ratio Products Ratio Products Ratio

C2+H 0.43 C2H+H 0.50 C2H2+H 0.29 C2H3+H 0.11 C2D4+D 0.12CH+C 0.39 C2+H2 0.02 C2H+H2 0.06 C2H2+H2 0.06 C2D3+D2 0.00C+C+H 0.18 C2+H+H 0.30 C2H+H+H 0.59 C2H2+H+H 0.66 C2D3+D+D 0.27

CH2+C 0.05 C2+H2+H 0.03 C2H+H2+H 0.10 C2D2+D2+D 0.28CH+CH 0.13 CH3+C 0.01 CH4+C 0.01 C2D2+D+D+D 0.13

CH2+CH 0.03 CH3+CH 0.02 C2D+D2+D2 0.00CH2+CH2 0.04 C2D+D2+D+D 0.00

CD4+CD 0.02CD3+CD2 0.17CD3+C+D2 0.00

C2D5+C2H

+ C2H2+ C2H3

+ C2H4+

Results have been compiled by Janev and Reiter (2002, 2004), and byFlorerscu-Mitchell and Mitchell (2006) and Adams, Poteryaand Babcock (2006)

Viggiano et al. 2005

CF2+ + e CF + F 714

CF3+ + e CF2 + F

8010Ehlerding et al. 2006

New theory: PRL 90, 133201 (2003), PRA 68, 012703 (2003)

CRYRING

2000

Theory

ke[cm3s-1]

2003

AISA

Kreckel et al., Phys. Rev. Lett. 95, 263201 (2005)

TSR

CRYRING

H3+

H3+ D3

+

D2H+ May 2007, CRYRING

-900 V/ring

electrode

H2

para

Gas inlet/2 atm

Solenoid valve

Pinhole flange/ground

electrode

Insulating spacer

Skimmer

Planned experimentPlanned experiment

Ion source will be characterised at the University of Illinois, in Ben McCall’s group with cavity ring-down spectroscopy; critical question: can we produce para-H3

+

using para-H2 as feed gas?

Experiment planned for September 2007, one week of beam time has been allocated

Advanced Intergrated Stationary AfterglowGlosik et al. 2005

Glosik et al. 2005

Summary HSummary H33++

Good agreement experiment-theory for dissociative recombination of H3

+, D3+ and H2D+

Several storage ring experiments agree with each other, but disagree with theory

Stationary afterglow experiments for H3+ give

almost factor 100 lower rate coefficient than storage rings and theory

Para-H3+ will be used in experiment in CRYRING