title: Isotopically selective infrared multiphoton dissociation of 2,3-dihydropyran.
abstract: Oxygen isotopic selectivity on infrared multiphoton dissociation of 2,3-dihydropyran has been studied by the examination of the effects of excitation frequency, laser fluence, and gas pressure on the dissociation probability of 2,3-dihydropyran and isotopic composition of products. Oxygen-18 was enriched in a dissociation product: 2-propenal. The enrichment factor of 18O and the dissociation probability were measured at a laser frequency between 1033.5 and 1057.3 cm-1, the laser fluence of 2.2-2.3 J/cm2, and the 2,3-dihydropyran pressure of 0.27 kPa. The dissociation probability decreases as the laser frequency being detuned from the absorption peak of 2,3-dihydropyran around 1081 cm-1. On the other hand, the enrichment factor increases with detuning the frequency. The enrichment factor of 18O increases with increasing the 2,3-dihydropyran pressure at the laser fluence of 2.7 J/cm2 or less and the laser frequency of 1033.5 cm-1, whereas the yield of 2-propenal decreases with increasing the pressure. A very high enrichment factor of 751 was obtained by the irradiation of 0.53 kPa of 2,3-dihydropyran at 2.1 J/cm2. Collisional effect of vibrationally excited molecules with ambient molecules on isotopic selectivity is discussed on the basis of a rate equation model including a collisional vibrational de-excitation process.
authors.affiliation: Quantum Beam Science Directorate, Japan Atomic Energy Agency, Naka-gun, Ibaraki, Japan. yokoyama.atsushi@jaea.go.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yokoyama
authors.forename: Keiichi
authors.initials: K
authors.lastname: Katsumata
authors.forename: Hironori
authors.initials: H
authors.lastname: Ohba
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Akagi
authors.forename: Morihisa
authors.initials: M
authors.lastname: Saeki
authors.forename: Keiichi
authors.initials: K
authors.lastname: Yokoyama