Dissociative recombination Dissociative recombination of CHof CH22OHOH++ and CD and CD22ODOD++

Mathias HambergMathias HambergWolf Geppert, Richard Thomas

Fabian Österdahl, Vitaly Zhaunerchyk, Jacek Semaniak, Magdalena Kaminska

Magnus af Ugglas, Anders KällbergMats Larsson

Ion-electron processesIon-electron processes

AB+(v=n) + e- AB + h

Radiative recombination

(slow)

AB+(v≠n) + e-

Elastic and superelasticscattering

A+ + B-Resonant ion pair

formationA + B

Dissociative Recombination

(DR)

DR exampleDR example

+

e- e-

Direct processDirect process

AB**AB+

Internuclear separation

Pot

entia

l ene

rgy A+B+

A+B

Indirect processIndirect process

AB**AB+

Internuclear separation

Pot

entia

l ene

rgy AB* A+B+

A+B

A+B

Where can Where can we we find find Dissociative recombination Dissociative recombination process ?process ?

•Comas of comets•The northern lights•Dark clouds•Tukamak plasma’s•Lightning

WhWhyy CHCH22OHOH++ and CD and CD22ODOD+ + ??

•Alcohols are fun So are their products

•Previous investigations about methanol

•Significant pathways for production and destruction of: NH4

+, NH3, H2O, H3O+ Pathways competes with DR-reaction

How and whatHow and what

•JIMIS hollow cathode ion source•Isomerization?•Symmetries, energy barrier?

HydroxymethHydroxymethylyl

ionion

CHCH22OHOH+ +

Methoxy ionMethoxy ion

CHCH22OHOH+ +

CRYRINGCRYRING

Formation of the ions with

JIMIS

Mass selection with bending

magnet

RFQInjection

Acceleration via RF

e--coolerCooling and

interaction region

Detection of neutrals with

SBD

ee---cooler-cooler

DetectionDetection

Branching RatiosBranching Ratios

Spectrum for CHSpectrum for CH22OHOH++

Spectrum for CDSpectrum for CD22ODOD++

Difficultto

resolve

Branching RatiosBranching Ratios

Reaction channels:Reaction channels:

CHCH22OHOH++ CDCD22ODOD++

CHCHxxOO CD CDxxO O αα

HH22O + CH O + CH DD22O + CD O + CD ββ

CHCH22 + OH + OH CDCD22 + OD + OD γγ

αα: : non non C-O bondbreakingC-O bondbreakingββ, , γγ:: C-O bondbreaking C-O bondbreaking

TransmissionTransmission

probabilityprobability

T=0.297T=0.297

Branching RatiosBranching Ratios

Measured counts for Measured counts for CHCH22OHOH++

αα ββ γγ

Branching RatiosBranching Ratios

CHCH33OO++ : : CDCD33OO+ + : :

CHCHxxOO++ (98%) (98%) CDCDxxOO+ (+ (92%) 92%) αα

HH22O + CH (0.7%)O + CH (0.7%)DD22O + CD (2%)O + CD (2%) ββ

CHCH22 + OH (1.6%) + OH (1.6%) CDCD22 + OD (6%) + OD (6%) γγ

Contrary to the CHContrary to the CH33OHOH22++ ion, the pathways ion, the pathways

preserving the bond between the heavypreserving the bond between the heavyatoms dominate.atoms dominate.

Reaction cross sectionReaction cross section

Ramping the cathode voltagelinearly according to the figure

The following spectrum was achieved

Cooling

1 eV

coolecm EEE

Reaction cross sectionReaction cross section

•Preliminary evaluation of the data yielded a reaction rate coeffecient of

•CH2OH+

6.8*10-7 (T/300) -0.63 cm3mol-1s-1

•CD2OD+

8.4*10-7 (T/300) -0.62 cm3mol-1s-1

•Error bars < 15%, biggest factor is the ion current measurement

Results?

DiscussionDiscussion

• Contrary to the CHContrary to the CH33OHOH22++ ion, the pathways ion, the pathways

preserving the bond between the heavy atoms preserving the bond between the heavy atoms dominatedominate

• Why? C-O bond has double bond character, although Why? C-O bond has double bond character, although DR is known to often break strong bondsDR is known to often break strong bonds

• Further investigations will take place in order to Further investigations will take place in order to increase the resolution and resolve the different increase the resolution and resolve the different CDCDxxOO++ channelschannels

• Isomerization: Hydroxymethyl ion CHIsomerization: Hydroxymethyl ion CH22OHOH++ likely to be likely to be dominating during the measurementsdominating during the measurements

• Overall impact: Results might be used within Overall impact: Results might be used within astrochemical modelsastrochemical models

CreditsCredits

•Wolf Geppert•Mats Larsson•Fabian Österdahl•Vitali Zhaunerchyk•Richard Thomas, •Magnus af Ugglas•Anders Källberg•Ansgar Simonsson ,and the rest of the CRYRING-crew