A variable geometry photofragment spectrometer

Johnson, Nigel P.; Barry, Martin; Gorry, P.A.

doi:10.1088/0022-3735/19/10/010

Cited by 8 publications

(8 citation statements)

References 18 publications

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“…In this case the LAB angular distribution can be expressed, to a reasonable approximation, as a phase shifted version of equation (1) 1- 32,25]. The phase shift is easily seen in figure 1.…”

Section: Resultsmentioning

confidence: 99%

“…The apparatus, a recently constructed high resolution variable geometry pulsed beam photofragment spectrometer, has been described in detail elsewhere [6,25] and will only be dealt with briefly here. It consists of three main parts; a source chamber, a scattering chamber, and a triply differentially pumped UHV [26] providing gas pulses of FWHM ~ 40/Is operating at 56 Hz--twice the laser repetition rate.…”

Section: Methodsmentioning

confidence: 99%

“…The angular distribution of the I atoms were carried out using an intra-cavity five stack pile-of-plates polarizer [25] to produce in excess of 99 per cent polarization in the laser output; as measured by external crossed ten stack polarizers. The plane of polarization is rotated using a pair of back-to-back Fresnel rhombs.…”

Section: Methodsmentioning

confidence: 99%

“…We report here a study of the photodissociation dynamics of C2HsI and CFaCH2I at 248 nm performed using our new variable-geometry, pulsed supersonic molecular beam photofragment spectrometer incorporating a 50cm flight path [25]. Future papers will examine the propyl and butyl iodides and their substituted counterparts.…”

Section: Introductionmentioning

confidence: 99%

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Photofragmentation dynamics of C₂H₅I and CF₃CH₂I at 248 nm

1987

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Translational photofragment spectroscopy has been used to study the photodissociation dynamics of C2HsI and CF3CH2I at 248nm. The measured anisotropies of the photofragments show that the initial absorption is the (parallel polarized) 3Q0 ,--N transition with a dissociation lifetime of 4 + 2 x 10-13s in both cases. The time of flight measurements yield the energy disposal for channels leading to I (2P3/2) and I* (2p1/2) for both molecules. The average energy disposed into translation is 62 per cent (I) and 72 per cent (I*) for C2HsI, and 36 per cent (I) and 39 per cent (I*) for CFaCH2I. The quantum yield for I* production is 0-67 + 0"03 for C2HsI and 0"82 + 0-07 for CFaCH2I. The results, combined with those of other workers, are compared to an impulsive description of the dissociation dynamics for a variety of substituted alkyl iodides. Finally a simple LandauZener curve crossing model is used to highlight the substantial change in curve crossing probability caused by introduction of fluorine atoms at the fl position.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photofragmentation dynamics of C₂H₅I and CF₃CH₂I at 248 nm

1987

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“…The apparatus has been described in detail elsewhere [1,12] and will only be dealt with briefly here. It consists of three main parts; a source chamber, a scattering chamber, and a triply differentially pumped UHV detection system.…”

Section: Methodsmentioning

confidence: 99%

Photofragmentation dynamics of n-C₃H₇I and i-C₃H₇I at 248 nm

1987

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Translational photofragment spectroscopy has been used to study the photodissociation dynamics of n-C3HTI and i-C3HTI at 248 nm. The measured anisotropies of the photofragments show that the initial absorption is the (parallel polarized) 3Qo*--N transition with a dissociation lifetimes of 3.7 + 2 x 10 13s and 2.5 + 2 x 10-13s respectively. The time of flight measurements yield the energy disposal for channels leading to I(2P3/2) and I*(2P1/2) for both molecules, although with greater uncertainty for i-C3H7I. The average energy disposed into translation is 43 per cent (I) and 52 per cent (I*) for n-C3H7I , and 39 per cent (I) and 57 per cent (I*) for i-C3H7I.The energy disposal for a variety of alkyl iodides are found to be well described by an impulsive model of the dissociation dynamics with the niodoalkanes showing a near constant width for the translational energy distribution regardless of its absolute value. A simple Landau-Zener curve crossing description is used to highlight the substantial change in curve crossing probability caused by substitution at the fl carbon or change to a secondary structure for the radical. Finally a model which combines the soft-radical impulse model for energy disposal with the Landau-Zener curve crossing probability is found to provide an excellent description of the I* quantum yields for the n-iodoalkanes.

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