Two-photon dissociation dynamics of small halogenated and related molecules using photofragment imaging technique = 작은 할로겐화 및 유관 분자들의 광분해체 영상장치를 이용한 이광자 해리 반응 동력학

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Two-photon Dissociation Dynamics of $Br_2$ near 234 nm The photodissociation of $Br_2$ has been investigated using a velocity map imaging technique via two-photon excitation at wavelengths in the range 229.4 - 237.6 nm. Analysis of the ion images illustrated that some fragmented bromine atoms were in highly excited Br(5s$\rm ^2P_J$: J = 5/2, 3/2, 1/2) states, which are caused by the dissociation of superexcited states populated via two-photon excitation. These highly excited neutral states over the ionization potential were characterized to have various asymptotes composed of Br(4p$\rm ^2P_J$: J = 3/2, 1/2) + Br(5s$\rm ^2P_{J`}, J`$ = 5/2, 3/2, 1/2) and suggested to be [$\rm ^2∏_{u,1/2 or 3/2}]_c5p_u$ using quantum defect formula. Unlike the previous imaging study on multiphoton excitation of $Br_2$,two-photon excitation in this work has been suggested to proceed to direct dissociation and compete with direct ionization or autoionization. Ion-pair Dissociation Studies of $CH_3$Br via Two-Photon Excitation at 234 nm The ion-pair state of methyl bromide has been attained by two-photon excitation at 234 nm. Velocity map image of fragmented $CH_3^+$ ion showed weak vibrational structures, which was attributed to multimode vibration of methyl ion. The over threshold excitation competed with the dissociation at A-continuum reached by one photon absorption and multimode excitation of $CH_3^+$ vibration was understood by possible accessibility to the wide window of Franck-Condon region while the over threshold excitation. Two other mechanisms, {\it i.e.} superexciation following dissociation and dissociative ionizaiton, were also examined as candidates of methyl ion producing processes. However thermodynamic considerations and investigation of cofragment $Br^+$ ion images proved that ion-pair formation was the principal source of the observed methyl ions. Vacuum ultraviolet photochemistry of methane, silane and germane The photochemistry of jet-cooled $CH_4$, $SiH_4...
Jung, Kyung-Hoon정경훈
한국과학기술원 : 화학과,
Issue Date
174673/325007 / 000975826

학위논문(박사) - 한국과학기술원 : 화학과, 2002.2, [ x, 92 p. ]


bromine; ch3br; imaging; dissociation; two-photon; 동력학; 레이저; 할로겐; 분해반응; 이광자

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