Photofragment translational spectroscopy

Ashfold, Michael N. R.; Lambert, Ian R.; Mordaunt, David H.; Morley, Gregory P.; Western, Colin

doi:10.1021/j100186a033

Cited by 108 publications

(55 citation statements)

References 2 publications

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“…The bands observed in the PA spectra are of di erent types and they represent the contributions resulting from the three dominant isotopomers [CHF 35 Cl 2 ]: [CHF 35 Cl 37 Cl]:[CHF 37 Cl 2 ] 9 :6 :1 according to the occurrence of the two stable Cl isotopes. These bands are related approximately to CH stretch overtones and to their combinations with bends and therefore possess di erent shapes, depending on the character of the involved vibrations.…”

Section: Hydrochloro¯uorocarbon Smentioning

confidence: 99%

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Bar¹,

Rosenwaks²

2001

International Reviews in Physical Chemistry

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Photodissociation studies of vibrationless ground state molecules pervade diverse areas of chemical physics, while those of rovibrationally excited molecules are expected to have even more impact due to the additional fascinating possibilities they o er and the new horizons they open. Photodissociation of rovibrationally excited species involves a double-resonance scheme in which a photodissociative transition is initiated from an excited rovibrational state that might substantially a ect the intensity and wavelength dependence of the photoabsorption spectrum. In favourable cases, when the energy is disposed in vibrations that are strongly coupled to the reaction coordinate, this pre-excitation might in¯uence photodissociation pathways and lead to selective bond cleavage. In other cases it might in¯uence the branching ratio between di erent fragments by altering the photodissociation dynamics. Moreover, the photodissociation of rovibrationally excited species can serve as a sensitive means for detection of weak vibrational overtone transitions of jet-cooled molecules, and therefore a promising way for revealing speci®c couplings and time evolution of the prepared vibrational states. Experimental studies on di erent polyatomics are used to demonstrate the above aspects and to show how the mechanism of chemical transformations and the nature of rovibrationally excited states are highlighted by photolysis of these pre-excited molecules.

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Section: Hydrochloro¯uorocarbon Smentioning

confidence: 99%

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Bar¹,

Rosenwaks²

2001

International Reviews in Physical Chemistry

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“…For example, nascent bromine atom will destroy ozone in the stratosphere via the BrO catalytic cycle 1 and it is mainly produced by solar ultraviolet ͑UV͒ photodissociation of natural, agricultural, and industrial bromocompounds. Photofragment translational spectroscopy ͑PTS͒ [2][3][4][5][6] has provided an ideal tool to investigate these photodissociation dynamics in a collision-free regime, in which any neutral photofragments ͑stable molecule or reactive radical͒ can be detected. In these experiments one can obtain product state, branching ratio, fragments translational energy distribution, and angular distribution of photofragments, thus one can get the energy distribution relationship between translational and internal energy.…”

Section: Introductionmentioning

confidence: 99%

Photodissociation of bromobenzene at 266 nm

Zhang

Zhu

Wang

et al. 1999

The Journal of Chemical Physics

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The photodissociation of C 6 H 5 Br at 266 nm has been investigated on the universal crossed molecular beam machine, and time-of-flight spectra as well as the angular distribution of Br atom have been measured. Photofragment translational energy distribution P(E t ) reveals that about 47% of the available energy is partitioned into translational energy. The anisotropy parameter ␤ at this wavelength is Ϫ0.7Ϯ0.2. From P(E t ) and ␤, we deduce that C 6 H 5 Br photodissociation is a fast process and the transition dipole moment is almost perpendicular to the C-Br bond. Ab initio calculations have been performed, and the calculated results show that the geometry of the first excited state of bromobenzene has changed apparently compared with that of the ground state. Two kinds of possible fast dissociation mechanism have also been proposed.

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“…Such conclusions were reiterated in a more recent study of the Doppler lineshape of the resulting H atom photofragments (26). However, any quantitative understanding of the energy disposal in this dissociation, and its specific dependence on parent quantum state, had to await the development of the technique of H atom photofragment translational spectroscopy by Welge and co-workers (27)(28)(29)(30)(31)(32). The time-of-flight (TOF) spectra of the H atoms resulting from photodissociation of NH3 following excitation to each of a number of vibronic levels of the A'A; state showed well resolved struture.…”

Section: Introductionmentioning

confidence: 99%

Near ultraviolet photolysis of phosphine studied by H atom photofragment translational spectroscopy

Lambert¹,

Morley²,

Mordaunt³

et al. 1994

Can. J. Chem.

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. Can. J. Chem. 72,977 (1 994).We report time-of-flight measurements of the H atom fragments arising in the photodissociation of phosphine at three near ultraviolet excitation wavele_ngths -2 18.2 nm, 221.6 nm, and 228.0 nm. For these wavelengths, energetic considerations dictate that ground state PH2(X) fragments must be the partner product of the primary photolysis event. The measured H atom kinetic energy distributions indicate that internal excitation of these partner fragments accounts for the major part (362%) of the available energy, in excess of that required to break the H-pH2 bond, provided by the photon. Inspection of the poorly resolved structure evident near the peak of the H atom kinetic energy distribution suggests the presence of substantial bending excitation and a-axis rotational excitation in the pH2 partner fragment. The_H atom kinetic energy distribution also shows clear evidence of atoms arising from secondary photolysis of the primary PH,(X) fragments. This second_ary photo-dissociation is observed to show a marked anisotropy, consistent with a perpendicular photo-excitation of the PH2(X) fragment. Arguments are presented which indicate that the secondary photolysis leads both to the formation of PH(X) fragments, carrying high levels of rotational excitation, and to the three-body atomisation process. On a effectuC des mesures en temps de vol des atomes d'hydrogkne, sous la forme de fragments provenant de la photodissociation de la phosphine B trois longueurs d'onde d'excitation -218,2, 221,6 et 2230 nm -proches de l'ultraviolet. Pour ces longueurs d'onde, des considCrations CnergCtiques dictent que les fragments PH2(X) de 1'Ctat fondamental doivent Etre les produits partenaires de la photolyse primaire. Les distributions de l'knergie cinCtique mesurCes pour les atomes d'hydrogbne indiquent que l'excitation interne de ces fragments partenaires tient compte de la plus grande partie (362%) de 1'Cnergie disponible B partir du photon, ce qui est supCrieur B 1'Cnergie requise pour briser la liaison H-pH2. Un examen minutieux de la structure ma1 rCsolue prCsente prks du pic de la distribution de 1'Cnergie cinCtique des atomes d'hydrogkne suggkre la prCsence d'une excitation importante de dkformation et d'une excitation rotationnelle le long de l'axe a du fragment partenaire pH2. La distribution de 1'Cnergie cinCtique des_atomes d'hydrogkne montre des preuves de la prCsence d'atomes provenant d'une photoIyse secondaire des fragments PH2(X) primaires. L'observation de cette photodissoc~ation secondaire dCmontre la prCsence d'une anisotropie marquCe qui est en accord avec une photoexcitation du fragment PH2(X). On prCsente des arguments indiquant que la photolyse secondaire conduit B la formation de fragments PH(X) portant des niveaux ClevCs d'excitation rotationnelle ainsi qu'au processus d'atomisation B trois corps.[Traduit par la redaction]

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Photofragment translational spectroscopy

Cited by 108 publications

References 2 publications

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Controlling bond cleavage and probing intramolecular dynamics via photodissociation of rovibrationally excited molecules

Photodissociation of bromobenzene at 266 nm

Near ultraviolet photolysis of phosphine studied by H atom photofragment translational spectroscopy

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