Ultraviolet photodissociation dynamics of the n-propyl and i-propyl radicals

Journal Article · Sun Jun 14 00:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4922311· OSTI ID:22415970

Song, Yu; Zheng, Xianfeng; Zhou, Weidong; Lucas, Michael; Zhang, Jingsong ^[1]

---

1. Department of Chemistry, University of California at Riverside, Riverside, California 92521 (United States)

Ultraviolet (UV) photodissociation dynamics of jet-cooled n-propyl (n-C{sub 3}H{sub 7}) radical via the 3s Rydberg state and i-propyl (i-C{sub 3}H{sub 7}) radical via the 3p Rydberg states are studied in the photolysis wavelength region of 230–260 nm using high-n Rydberg atom time-of-flight and resonance enhanced multiphoton ionization techniques. The H-atom photofragment yield spectra of the n-propyl and i-propyl radicals are broad and in good agreement with the UV absorption spectra. The H + propene product translational energy distributions, P(E{sub T})’s, of both n-propyl and i-propyl are bimodal, with a slow component peaking around 5-6 kcal/mol and a fast one peaking at ∼50 kcal/mol (n-propyl) and ∼45 kcal/mol (i-propyl). The fraction of the average translational energy in the total excess energy, 〈f{sub T}〉, is 0.3 for n-propyl and 0.2 for i-propyl, respectively. The H-atom product angular distributions of the slow components of n-propyl and i-propyl are isotropic, while that of the fast component of n-propyl is anisotropic (with an anisotropy parameter ∼0.8) and that of i-propyl is nearly isotropic. Site-selective loss of the β hydrogen atom is confirmed using the partially deuterated CH{sub 3}CH{sub 2}CD{sub 2} and CH{sub 3}CDCH{sub 3} radicals. The bimodal translational energy and angular distributions indicate two dissociation pathways to the H + propene products in the n-propyl and i-propyl radicals: (i) a unimolecular dissociation pathway from the hot ground-state propyl after internal conversion from the 3s and 3p Rydberg states and (ii) a direct, prompt dissociation pathway coupling the Rydberg excited states to a repulsive part of the ground-state surface, presumably via a conical intersection.

• OSTI ID: 22415970
• Journal Information: Journal of Chemical Physics, Vol. 142, Issue 22; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTRA
ANGULAR DISTRIBUTION
ATOMS
COUPLING
DISSOCIATION
ENERGY SPECTRA
GROUND STATES
HYDROGEN
INTERNAL CONVERSION
PHOTOIONIZATION
PHOTOLYSIS
PROPYL RADICALS
PROPYLENE
RYDBERG STATES
TIME-OF-FLIGHT METHOD
ULTRAVIOLET RADIATION