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ThesisUniversity of Iceland>Verkfræði- og náttúruvísindasvið>B.S. verkefni>

Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/7544

Title

2D-REMPI of CF3Br: Spectroscopy and Dynamics

Published
February 2011
Abstracts
  • is

    (2+n) REMPI litróf af CF3Br fyrir jónirnar CF3+ og iBr+ (i = 79, 81) var skráð fyrir örvunarorkurnar 71 320 – 84 600 cm-1. 1D-REMPI litróf fyrir mældu jónabrotin var svo fengið með því að heilda 2D-REMPI litrófið sem fékkst úr mælingunum. Einungis sáust merki fyrir CF3+, C+ og 79,81Br+ á þessu svæði og síðari tvö merkin voru ósamfelld og gáfu einungis skarpar atómlínur. Kolefnis og bróm atómlínurnar voru bornar saman við viðurkennd gildi úr NIST atómlínu gagnabankanum og var mismunurinn á milli atómlína þar sem hann var mestur rúm 0.01 %. Merkið frá CF3+ sást einungis fyrir þær örvunarorkur þar sem CF3Br sameindin var örvuð á [X2E] 5p Rydberg ástand af frá grunnástandi. Færslur 4p -> 5s sáust ekki vegna lítilla færslulíkinda þar sem færslan fylgir ekki valreglunni fyrir tveggja-ljóseinda örvun: ∆l = 0, ±2.
    Samfellt CF3+ merki og sterkar bróm atómlínur gefa til kynna að aðal ljósklofnunar ferill CF3Br sé brot á C-Br tenginu og myndun CF3 + Br stakeinda í gegnum fráhrindandi ástand. Klofnun í gegnum jónpara ástand sást einnig, auk myndunar á flúrljómandi CF3* sameind. Aflháðar mælingar voru gerðar fyrir CF3+ merkið sem staðfestu að það var tilkomið vegna klofnunar í gegnum jónpara ástand.

  • (2+n) REMPI spectra of CF3Br for the ions CF3+ and iBr+ ( i = 79, 81) was recorded for the excitation energy region 71 320 – 84 600 cm-1. 1D-REMPI spectra for the measured ion fragments were constructed by integrating the 2D-REMPI spectra obtained from the measurements. Only CF3+, C+ and 79,81Br+ signals were observed during the measurements. The latter two ion fragment signals being non-continuous yielding only sharp atomic line peaks. The carbon and bromine atomic lines were compared to the NIST atomic line database and showed good agreement with the accepted values with a maximum error of about 0.01 %. The signal from CF3+ was only observed in the excitation energy region where the CF3Br molecule was excited to a [X2E] 5p Rydberg state from a ground state. Transitions 4p -> 5s were not observed due to the low transition probability since the transition does not follow the selection rule for two-photon excitation: ∆l = 0, ±2.
    Continuous CF3+ signal and strong bromine atomic lines would indicate that the major photodissociation mechanism of CF3Br is breaking of the C-Br bond and the formation of CF3 + Br radicals via a repulsive state. Dissociation via ion-pair state was observed aswell as the formation of a fluorescent CF3* species. Power dependence measurements were done on the CF3+ signals which confirmed that the signal observed was from CF3+ formed via ion-pair state dissociation.

Issued Date
08/02/2011


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