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

Task for Stockholm according to minutes of 2005 BeH + and BeH 2 + Problem: The Manne Siegbahn Laboratory reluctant to deal with Be.

Some 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 The decision to shut down the lab was taken 2002, so the damage control has been quite successful! Beam time during 2008 unclear

Progress Experiment on C 4 D 2 + Results on CF 2 + and CF 3 + The H 3 + and its isotopologues Development of data base for dissociative recombination

Doubly excited neutral molecule A 2 +B AB+A A+A+B + e-e- DR of polyatomic ions A 2 B + + e - (E e ) For example: C 2 H + + e -  C 2 + H eV  CH + C eV  C + C + H 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 C 2 H +, C 2 H 2 +, C 2 H 3 +, C 2 H 4 +, C 2 D 5 + C 3 H 4 +, C 3 H 7 +, C 4 D 9 +, C 4 D 2 +), CF n +, H 3 +

Manne Siegbahn Laboratory 52 meters circumference

Experiment 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)

A e  A + A; no grid 2A Energy Pulse height spectrum

A 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 fraction measurement C 2 H + +e -

Relate the fragments to different dissociation channels! C 2 H + +e - 2C C+H C 2C+H DR Branching ratio measurement C 2 H + + e -  C 2 + H  CH + C  C + C + H

DR Branching ratios – Hydrocarbon ions DR Branching ratios – Hydrocarbon ions Results have been compiled by Janev and Reiter (2002, 2004), and by Florerscu-Mitchell and Mitchell (2006) and Adams, Poterya and Babcock (2006)

Viggiano et al. 2005

CF e  CF + F 71  4 CF e  CF 2 + F80  10 Ehlerding et al. 2006

New theory: PRL 90, (2003), PRA 68, (2003) CRYRING 2000 Theory keke [cm 3 s -1 ] 2003 AISA

Kreckel et al., Phys. Rev. Lett. 95, (2005) TSR CRYRING H3+H3+

H3+H3+ D3+D3+

D 2 H + May 2007, CRYRING

-900 V/ring electrode H 2 para Gas inlet/ 2 atm Solenoid valve Pinhole flange/ground electrode Insulating spacer Skimmer

Planned 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-H 3 + using para-H 2 as feed gas? Experiment planned for September 2007, one week of beam time has been allocated

Advanced Intergrated Stationary Afterglow Glosik et al. 2005

Summary H 3 + Good agreement experiment-theory for dissociative recombination of H 3 +, D 3 + and H 2 D + Several storage ring experiments agree with each other, but disagree with theory Stationary afterglow experiments for H 3 + give almost factor 100 lower rate coefficient than storage rings and theory Para-H 3 + will be used in experiment in CRYRING