Selective Photodissociation of Condensed and Adsorbed SmallMolecules by Specific Core‐to‐Bound Excitations: Evidence forUltrafast Dissociation Channels
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Medientyp:
E-Artikel
Titel:
Selective Photodissociation of Condensed and Adsorbed SmallMolecules by Specific Core‐to‐Bound Excitations: Evidence forUltrafast Dissociation Channels
Beteiligte:
Menzel, Dietrich
Erschienen:
Wiley, 1991
Erschienen in:
Laser Chemistry, 11 (1991) 3-4, Seite 231-235
Sprache:
Englisch
DOI:
10.1155/lc.11.231
ISSN:
0278-6273;
1476-3516
Entstehung:
Anmerkungen:
Beschreibung:
The modification of photodissociation mechanisms of small molecules by adsorption on a solid or bycondensation is briefly reviewed. The coupling to the surroundings leads to quenching of easilydelocalizable primary excitations so that only strongly localized channels show up in dissociation (detectedby photodesorption, i.e. by the appearance of fragments in the gas phase). In reverse, fast directdissociation channels will be less in need of such localization and will be preferred over slow channels.Investigation of dissociation induced by core excitations or core shake‐ups introduces an internal timemark—core life time—to which reaction time can be compared. The example of small molecules, such asCO or NO, adsorbed on transition metal surfaces is surveyed, in which complex multiple excitationspredominate in dissociation. Recent results on the core‐induced dissociation of condensed hydrogenicmolecules such as water, ammonia, and benzene have shown the existence of preferential dissociationchannels in the core‐to‐bound region. It is argued that these dissociation processes are at least competitivewith core decay; they are termed ultrafast. It appears that they should also exist in the freemolecules.