skip to main content

Title: Evidence of CH{sub 2}O (a-tilde{sup 3}A{sub 2}) and C{sub 2}H{sub 4} (a-tilde{sup 3}B{sub 1u}) produced from photodissociation of 1,3-trimethylene oxide at 193 nm

We investigated the dissociative ionization of formaldehyde (CH{sub 2}O) and ethene (C{sub 2}H{sub 4}) produced from photolysis of 1,3-trimethylene oxide at 193 nm using a molecular-beam apparatus and vacuum-ultraviolet radiation from an undulator for direct ionization. The CH{sub 2}O (C{sub 2}H{sub 4}) product suffers from severe dissociative ionization to HCO{sup +} (C{sub 2}H{sub 3}{sup +} and C{sub 2}H{sub 2}{sup +}) even though photoionization energy is as small as 9.8 eV. Branching ratios of fragmentation of CH{sub 2}O and C{sub 2}H{sub 4} following ionization are revealed as a function of kinetic energy of products using ionizing photons from 9.8 to 14.8 eV. Except several exceptions, branching ratios of daughter ions increase with increasing photon energy but decrease with increasing kinetic energy. The title reaction produces CH{sub 2}O and C{sub 2}H{sub 4} mostly on electronic ground states but a few likely on triplet states; C{sub 2}H{sub 4} (a-tilde{sup 3}B{sub 1u}) seems to have a yield greater than CH{sub 2}O (a-tilde{sup 3}A{sub 2}). The distinct features observed at small kinetic energies of daughter ions are attributed to dissociative ionization of photoproducts CH{sub 2}O (a-tilde{sup 3}A{sub 2}) and C{sub 2}H{sub 4} (a-tilde{sup 3}B{sub 1u}). The observation of triplet products indicates that intersystem crossing occursmore » prior to fragmentation of 1,3-trimethylene oxide.« less
Authors:
; ;  [1] ;  [2]
  1. National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)
  2. (China)
Publication Date:
OSTI Identifier:
20783229
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 124; Journal Issue: 7; Other Information: DOI: 10.1063/1.2170084; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; DISSOCIATION; ETHYLENE; FAR ULTRAVIOLET RADIATION; FORMALDEHYDE; FRAGMENTATION; GROUND STATES; KINETIC ENERGY; MOLECULAR BEAMS; PHOTOIONIZATION; PHOTOLYSIS; PHOTON-MOLECULE COLLISIONS; TRIPLETS; WIGGLER MAGNETS