ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The formation of C2H− is observed in two broad resonance bands when C2H2 is irradiated with vuv light. The higher-energy band has partially resolved structure, approximately linear pressure dependence, and a threshold at 16.335±0.021 eV. It is attributed to photoion-pair formation (C2H−+H+) consequent upon predissociation of one or more Rydberg states. This threshold, together with IP(H) and EA(C2H), gives D0(HCC–H)≤5.706±0.022 eV≡131.6±0.5 kcal/mol, or ΔH0f0 (C2H)≤134.5±0.5 kcal/mol. The lower-energy band has an approximately quadratic pressure dependence and curved step-like structure. It is attributed to photoelectron-induced dissociative attachment mediated by a πg shape resonance. The threshold, at 878.5±2.0 A(ring), corresponds to a photoelectron energy of 2.715±0.032 eV. This threshold combined with EA(C2H)=2.969±0.010 eV, yields D0(HCC–H)≤5.684±0.033 eV≡131.1±0.7 kcal/mol, or ΔH0f0 (C2H)=134.0±0.7 kcal/mol.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.459629
