ISSN:
1089-7690
Quelle:
AIP Digital Archive
Thema:
Physik
,
Chemie und Pharmazie
Notizen:
The photochemical carbon–halogen bond cleavage of CH3 Cl and CD3 Br, adsorbed on Pt(111) at 100 K, has been studied. These two adsorbates, which do not decompose thermally, are readily photodissociated, either alone or coadsorbed, when irradiated with the full spectrum of a 100 W high-pressure Hg arc. Just as in the gas phase, the dissociation products are methyl groups and halogen atoms. These species are identified using high resolution electron energy loss spectroscopy (HREELS), temperature programmed desorption (TPD), and Auger electron spectroscopy (AES). With wavelengths below 300 nm removed with a cutoff filter, irradiation of coadsorbed layers breaks only C–Br bonds. Using substrate temperatures of 65 K and coadsorbed Xe, the absence of significant local heating effects is clearly demonstrated. These results show that the photodissociation process is molecule specific and that the time scale for excited state quenching is, for methyl chloride and methyl bromide, not significantly faster than the time scale for significant bond elongation.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.457602
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