Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Experimental studies on the dissociative recombination of H13CO+ with electrons at energies between 2 – 50 000 meV
Stockholm University, Faculty of Science, Department of Physics. (Molekylfysik)
Stockholm University, Faculty of Science, Department of Physics. (Molekylfysik)
(Molekylfysik)
Stockholm University, Faculty of Science, Department of Physics. (Molekylfysik)
Show others and affiliations
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Determination of dissociative recombination processes of H13CO+ using merged ion-electron beam methods has been performed at the heavy storage ring CRYRING, Stockholm, Sweden. We have measured the branching fractions at ~0 eV as: CO+H 87±2%, OH+C 9±2% and O+CH 4±2%. The channels leading to CO+H have the following branching fractions between the accessible electronic states of CO(X1S+)+H 46±3%, CO(a3Pg)+H 20±1% and CO(a’3S+)+H 34±3% respectively. The reaction cross section was fitted between 1-300 meV and followed the expression σ = 1.2±0.25×10-16 E-1.32±0.02 cm2 and the corresponding thermal rate constant was determined to k(T) = 2.0±0.4×10−7(T/300)−0.82±0.02 cm3s−1. The cross sections between ~2-50 000 meV were investigated showing resonant structures between 3-15 eV.

Keyword [en]
H13CO+, HCO+, Dissociative recombination, Cross section, Branching fraction, Imaging, Storage ring, CRYRING
National Category
Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
URN: urn:nbn:se:su:diva-38760OAI: oai:DiVA.org:su-38760DiVA: diva2:314598
Available from: 2010-04-30 Created: 2010-04-27 Last updated: 2010-05-19Bibliographically approved
In thesis
1. Dissociative Recombination of Astrochemically Interesting Ions
Open this publication in new window or tab >>Dissociative Recombination of Astrochemically Interesting Ions
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis the major work described concerns experimental determination of the dissociative recombination (DR) reaction for several molecular ions of astrochemical interest. DR is the process where an electron recombines with a molecular ion to form an excited neutral that disintegrates into two or more neutral fragments to release the gained excess energy. It is very efficient under cold conditions and therefore ubiquitously occurring in interstellar environments such as dark clouds and plays an important role in aeronomical plasmae, lightnings and in man-made plasmas such as in combustion engines and fusion reactors. Although DR reactions are crucial processes in all these environments, product branching fractions of DR reactions have proven to be very unpredictable and present one of the great remaining challenges for theoreticians. The experimental work includes determination of reaction rates and product distribution of DR of complex ions such as protonated alcohols and ethers. The following species have been investigated and are discussed in this thesis:

CH3OH2+ (protonated methanol), CD3OD2+ (deuteronated methanol), CD3OCD2+ (methoxymethyl cation), CD3CDOD+ (deuteronated acetaldehyde), CH3CH2OH2+ (protonated ethanol) and (CD3)2OD+ (deuteronated dimethyl ether).

The results of these measurements are used in astrochemical model calculations in which the rates used hitherto greatly have been based on educated guesses. Employing the outcome of the DR investigations of the CH3OH2+ and CD3OD2+ ions have shown a great impact on such models. The DR investigations have been followed up by astronomical observations. Theoretical models and laboratory experiments show that methanol should be formed from CO on cold grains. This scenario was tested by astronomical observations of gas associated with young stellar objects (YSOs). Two independent tests were showing consistency with methanol formation on grain surfaces.

Abstract [sv]

I den här avhandlingen redovisas mitt arbete som till stor del baseras på experimentell bestämning av dissociativa rekombinations (DR) processer för molekylära joner av astrokemiskt intresse. DR är en process där en elektron rekombinerar med en molekylär jon som splittras up i två eller fler neutrala fragment för att göra sig av med den extra energi som erhållits. Processen är väldigt effektiv i kalla miljöer varför den är allestädes återkommande i omgivningar som interstellära moln och kometkoman och spelar en betydande roll i aeronomiska plasman, blixturladdningar men även i mänskligt skapade plasman såsom de i förbränningsmotorer och fusionsreaktorer. Det har dock visat sig att produkt distributionsförhållandena från DR reaktioner är mycket oförutsägbara och kvarstår som en av de stora återstående utmaningarna för teoretiker. Det experimentella arbetet består av bestämning av reaktionshastigheter samt produktdistribution för DR av komplexa joner som protonerade alkoholer och etrar. De följande jonerna har blivit undersökta och diskuteras i denna avhandling:

CH3OH2+ (protonerad metanol), CD3OD2+ (deuteronerad metanol), CD3OCD2+ (metoxymetyl katjon), CD3CDOD+ (deuteronerad acetaldehyd), CH3CH2OH2+ (protonerad etanol) och (CD3)2OD+ (deuteronerad dimetyleter).

Resultaten av mätningarna används i astrokemiska modelberäkningar i vilka reaktionshastigheterna som hittills använts till stor del baserats på kvalificerade gissningar. Insättning av resultaten av CH3OH2+ och CD3OD2+ jonerna har visat sig ha en stor effekt på sådana modeller. DR undersökningarna har följts upp av astronomiska observationer. Teoretiska modeller och laboratorieundersökningar visar att metanol borde kunna formas från CO på kalla iskornsytor, detta scenario har testats med astronomiska observationer av gas som associeras med unga stjärnor. Två oberoende undersökningar visade på förenlighet med metanolformation på kornytor.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2010. 79 p.
Keyword
Dissociative Recombination, Astrochemistry
National Category
Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-38833 (URN)978-91-7447-089-5 (ISBN)
Public defence
2010-05-28, Svedbergssalen, sal FD5, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished  and had a status as follows: Paper 1: Manuscript. Paper 2: In press. Paper 3: Manuscript. Paper 5: Manuscript.Available from: 2010-05-06 Created: 2010-04-29 Last updated: 2011-12-27Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Hamberg, MathiasKashperka, Irynaaf Ugglas, MagnusZhaunerchyk, VitaliThomas, Richard D.Vigren, ErikKällberg, AndersSimonsson, AnsgarPaál, AndrásGeppert, Wolf
By organisation
Department of PhysicsThe Manne Siegbahn Laboratory
Atom and Molecular Physics and Optics

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 97 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf