Comparative study of the dissociative ionization of 1,1,1-trichloroethane using nanosecond and femtosecond laser pulses
Abstract
Changes in the laser induced molecular dissociation of 1,1,1-trichloroethane
(TCE) were studied using a range of intensities and standard laser wavelengths with
nanosecond and femtosecond pulse durations. TCE contains C-H, C-C and C-Cl bonds and
selective bond breakage of one or more of these bonds is of scientific interest. Using laser
ionization time of flight mass spectrometry, it was found that considerable variation of
fragment ion peak heights as well as changes in relative peak ratios is possible by varying
the laser intensity (by attenuation), wavelength and pulse duration using standard laser
sources. The nanosecond laser dissociation seems to occur via C-Cl bond breakage, with
significant fragmentation and only a few large mass ion peaks observed. In contrast,
femtosecond laser dissociative ionization results in many large mass ion peaks. Evidence is
found for various competing dissociation and ionization pathways. Variation of the
nanosecond laser intensity does not change the fragmentation pattern, while at high
femtosecond intensities large changes are observed in relative ion peak sizes. The total
ionization yield and fragmentation ratios are presented for a range of wavelengths and
intensities, and compared to the changes observed due to a linear chirp variation
URI
http://hdl.handle.net/10394/6053https://doi.org/10.3390/ijms11031114
http://www.mdpi.com/1422-0067/11/3/1114