Triatomic Photofragment Spectra. I. Energy Partitioning in NO2 Photodissociation

Busch, G. E.; Wilson, Kent R.

doi:10.1063/1.1677740

Cited by 466 publications

(182 citation statements)

References 28 publications

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“…Consequently, overtime it became a benchmark system for a variety of spectroscopic and dynamics studies concerning theoretical and experimental aspects of photodissociation, intramolecular vibrational redistribution, nonadiabatic couplings [1,2,3,4,5,6,7,8,9,10,11,12,13]. The numerous nonadiabatic interactions are reflected in a complex photodissociation dynamics.…”

Section: Introductionmentioning

confidence: 99%

Imaging fast relaxation dynamics of NO₂

et al. 2009

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Time-resolved spectroscopy combined with velocity map imaging technique have been used to investigate the multiphoton dynamics of NO 2 molecule. Two different pump-probe excitation schemes were used to explore different potential energy surfaces (PESs) located in the first dissociation region and in the Rydberg region around 9.2 eV. Integrated and energy resolved signals of NO + 2 , NO + and photoelectrons were recorded as a function of time. When exciting with 403 nm photons, the NO + signal exhibits an intriguing oscillatory behaviour with a period of 512 fs. The NO + and photoelectron kinetic energy distributions produced by this pump wavelength were cold, while those produced when employing 269 nm photons as pump were very rich, evidencing the presence of multiple excitation channels. A couple of sharp long lived photoion-photoelectron peaks represents the most salient feature of latter. They were assigned to an excitation by two 269 nm photons to a Rydberg state dissociating into NO(A 2 Σ + )+O( 3 P ). This NO + peak as well as another one located at 0 eV display very complex time dependencies including the signatures of two dissociation dynamics on timescales of 400 and 600 fs. The different pathways responsible of this temporal behaviour are discussed in view of shedding light onto the underlying multichannel multiphoton dynamics.

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Section: Introductionmentioning

confidence: 99%

Imaging fast relaxation dynamics of NO₂

et al. 2009

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“…In addition to helping clear up some questions about the acetylene and ethynyl molecules, the 193 nm photodissociation studies are useful for understanding the process itself and can reveal information about the potential energy surfaces of the states involved [16]. The C 2 H 2 dissociation is an especially interesting case because of the confusion of states in the C 2 H system [17].…”

Section: Introductionmentioning

confidence: 99%

193 nm photodissociation of acetylene

Balko¹,

Zhang²,

Lee³

1991

The Journal of Chemical Physics

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The product translational energy distribution P(ET) for acetylene photodissociation at 193 nm was obtained from the time-of-flight spectrum of the H atom fragments. The P(ET) shows resolved structure from the vibrational and electronic excitation of the C2H fragment; comparison of the translational energy release for given excited states of C2H with the known energy levels of these states gives D0(HCC–H)=131.4±0.5 kcal/mol. This value is in agreement with that determined previously in this group from analogous studies of the C2H fragment and with the latest experimental and theoretical work. The high resolution of the experiment also reveals the nature of C2H internal excitation. A significant fraction of the H atoms detected at moderate laser power were from the secondary dissociation of C2H. The P(ET) derived for this channel indicates that most of the C2 is produced in excited electronic states.

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“…suming formation of 2 P 3͞2 bromine atoms) † is 42, 53, and 68 kcal⅐mol Ϫ1 for p-, m-, and o-benzyne, respectively. We also assume that the kinetic energy of the two bromine atoms is negligible, according to the relative masses in an impulsive (19) ultrafast C-Br bond cleavage.…”

Section: Methodsmentioning

confidence: 99%

Femtosecond observation of benzyne intermediates in a molecular beam: Bergman rearrangement in the isolated molecule

Diau

Casanova

Roberts

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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In this communication, we report our femtosecond real-time observation of the dynamics for the three didehydrobenzene molecules (p-, m-, and o-benzyne) generated from 1,4-, 1,3-, and 1,2-dibromobenzene, respectively, in a molecular beam, by using femtosecond time-resolved mass spectrometry. The time required for the first and the second C-Br bond breakage is less than 100 fs; the benzyne molecules are produced within 100 fs and then decay with a lifetime of 400 ps or more. Density functional theory and high-level ab initio calculations are also reported herein to elucidate the energetics along the reaction path. We discuss the dynamics and possible reaction mechanisms for the disappearance of benzyne intermediates. Our effort focuses on the isolated molecule dynamics of the three isomers on the femtosecond time scale.A rynes have presented chemists with structural and synthetic challenges for more than half a century. After the structure proposal for 1,2-didehydrobenzene by Wittig (1) , the challenge to understand the behavior and properties of these reactive species has attracted large numbers of chemists and spawned a whole area of inquiry within chemistry (3, 4). Although the greatest effort has been in the study of 1,2-dehydrobenzene, the behavior and properties of the 1,3-and 1,4-isomers have recently been the subject of many studies (refs. 5 and 6; and ref. 7 and references therein). The 1,3-isomer has been characterized recently (5). The 1,4-isomer has gained special prominence because of its propensity to undergo Bergman rearrangement (8) and its relationship to several currently exciting antitumor agents such as neocarzinostatin and dynemicin A. Materials and MethodsThe femtosecond laser and molecular beam apparatus is described in detail elsewhere (ref. 9 and references therein). Briefly, a femtosecond laser system was integrated to a molecular beam apparatus with the capability of measuring time-offlight mass spectra. The amplified pulses were typically Ϸ80 fs, and the energy input was Ϸ150 J⅐pulse Ϫ1 at 615 nm. For the pump, the 615-nm output was frequency doubled. The probe beam, which ionizes the transient species, was passed to a computer-controlled translation stage for the time delay. Both pump and probe beams were appropriately attenuated to minimize background signals; no ionization was observed when the pump pulse was blocked, and the transients are for the enhanced ionization when both pump and probe pulses are present. 1,4-Dibromobenzene (98%), 1,3-dibromobenzene (97%), and 1,2-dibromobenzene (98%), all from Aldrich, were used without further purification. The mass spectra show their characteristic patterns, as discussed below. The theoretical work reported herein involves density functional theory (DFT) and ab initio methods and will be detailed in the Discussion section. Fig. 1 shows the femtosecond mass spectra of 1,4-dibromobenzene (Fig. 1 A), 1,3-dibromobenzene (Fig. 1B), and 1,2-dibromobenzene (Fig. 1C). The mass spectra are similar. The parent signals are characterized by three pea...

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Triatomic Photofragment Spectra. I. Energy Partitioning in NO2 Photodissociation

Cited by 466 publications

References 28 publications

Imaging fast relaxation dynamics of NO₂

Imaging fast relaxation dynamics of NO₂

193 nm photodissociation of acetylene

Femtosecond observation of benzyne intermediates in a molecular beam: Bergman rearrangement in the isolated molecule

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Triatomic Photofragment Spectra. I. Energy Partitioning in NO2 Photodissociation

Cited by 466 publications

References 28 publications

Imaging fast relaxation dynamics of NO2

Imaging fast relaxation dynamics of NO2

193 nm photodissociation of acetylene

Femtosecond observation of benzyne intermediates in a molecular beam: Bergman rearrangement in the isolated molecule

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Imaging fast relaxation dynamics of NO₂

Imaging fast relaxation dynamics of NO₂