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Proceedings Paper

Comparative study of hexamethyldisiloxane photofragmentation through multiphotonic and monophotonic processes
Author(s): Cristina M. Quintella; G. Gerson B. de Souza; M. Suely P. Mundim
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Paper Abstract

A comparative study of the hexamethyldisiloxane (HMDSO) molecule photofragmentation induced by laser multiphotonic (MPI) and synchrotron monophotonic (SR) processes is presented. The HMDSO sample was effusively expanded into the vacuum chamber and fragmented by either laser or synchrotron irradiation. The resulting ions were detected by a time-of- flight spectrometer using both electron-ion and ion-ion coincidence techniques. The parent ion has not been observed in both processes suggesting its instability. MPI induced fragmentation is characterized by a high ionic yield (IY) in the lighter fragments region. The MPI atomization is severe generating ions like C+ and Si+ that are absent from the SR spectra. The doubly-charged ions SiOSi(CH3)2++ and SiOSi(CH3)4++ are observed in the SR spectra. SR and MPI fragmentation have a common main route: the methyl group ejection yielding m/q equals 147,148,149 and m/q equals 15. The first presents a higher IY suggesting that the positive charge stays preferentially with the more massive fragment. Through MPI there is another route: the Si-O bond breakage yielding m/q equals 73,74,75 and m/q equals 89 (Si(CH3)3+ and OSi(CH3)3+. The metastable doubly charged ions were SiOSiC1,2,3,6Hn++ and OSiC3Hn++ in the SR case; and a wider fragment mass range was observed through MPI.

Paper Details

Date Published: 15 May 1998
PDF: 9 pages
Proc. SPIE 3271, Laser Techniques for State-Selected and State-to-State Chemistry IV, (15 May 1998); doi: 10.1117/12.308391
Show Author Affiliations
Cristina M. Quintella, Univ. Federal da Bahia (Brazil)
G. Gerson B. de Souza, Univ. Federal do Rio de Janeiro (Brazil)
M. Suely P. Mundim, Univ. Federal da Bahia (Brazil)

Published in SPIE Proceedings Vol. 3271:
Laser Techniques for State-Selected and State-to-State Chemistry IV
John W. Hepburn; Robert E. Continetti; Mark A. Johnson, Editor(s)

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