Velocity-map ion-imaging of the NO fragment from the UV-photodissociation of nitrosobenzene

Obernhuber, Thorsten; Kensy, Uwe; Dick, Bernhard

doi:10.1039/b302319b

Cited by 19 publications

(24 citation statements)

References 49 publications

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“…This technique yields detailed velocity distributions for each rovibrational state of the NO fragment. [17][18][19][20][21] In contrast to the study of Doppler profiles the VMI method is not limited by the linewidth of the probe laser, and can easily distinguish fragments in the same final state that result from different dissociation channels associated with different velocities and anisotropies. In fact, the Doppler profiles measured in previous work were not analyzed in terms of the velocity distribution, but only in terms of anisotropy.…”

Section: Introductionmentioning

confidence: 99%

The photodissociation dynamics of N-nitrosopyrrolidine from the first and second excited singlet states studied by velocity map imaging

Wenge

Kensy

Dick

2010

Phys. Chem. Chem. Phys.

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The photodissociation reaction of N-nitrosopyrrolidine isolated and cooled in a supersonic jet has been studied following excitation to the S(1) and S(2) electronic states. The nascent NO (X[combining tilde] (2)Pi((1/2),3/2), v, j) radicals were ionized by state-selective (1 + 1)-REMPI via the A(2)Sigma(+) state. The angularly resolved velocity distribution of these ions was measured with the velocity-map imaging (VMI) technique. Photodissociation from S(1) produces NO in the vibrational ground state and the pyrrolidine radical in the electronic ground state 1 (2)B. About 73% of the excess energy is converted into kinetic energy of the fragments. The velocity distribution shows a strong negative anisotropy (beta = -0.9) in accordance with the npi*-character of the S(0)--> S(1) transition. An upper limit for the N-NO dissociation energy of (14 640 +/- 340) cm(-1) is determined. We conclude that photodissociation from S(1) occurs very fast on a completely repulsive potential energy surface. Excitation into the S(2)pipi*-state leads to a bimodal velocity distribution. Two dissociation channels can be distinguished which show both positive anisotropy (beta = 1.3 and 1.6) but differ considerably in the total kinetic energy and the rotational energy of the NO fragment. We assign one channel to the direct dissociation on the S(2) potential energy surface, leading to pyrrolidine radicals in the excited electronic state 1 (2)A. The second channel leads to pyrrolidine in the electronic ground state 1 (2)B, presumably after crossing to the S(1) state via a conical intersection.

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Section: Introductionmentioning

confidence: 99%

The photodissociation dynamics of N-nitrosopyrrolidine from the first and second excited singlet states studied by velocity map imaging

Wenge

Kensy

Dick

2010

Phys. Chem. Chem. Phys.

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“…As with several other reported spectrometer designs, [30][31][32][33][34][35][36] the ion optics assembly described in Ref. 25 provided a convenient starting point.…”

Section: A the New Ion Optics Assemblymentioning

confidence: 99%

Near ultraviolet photochemistry of 2-bromo- and 2-iodothiophene: Revealing photoinduced ring opening in the gas phase?

Marchetti

Karsili

Kelly

et al. 2015

The Journal of Chemical Physics

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Velocity map imaging methods, with a new and improved ion optics design, have been used to explore the near ultraviolet photodissociation dynamics of gas phase 2-bromo- and 2-iodothiophene molecules. In both cases, the ground (X) and spin-orbit excited (X*) (where X = Br, I) atom products formed at the longest excitation wavelengths are found to recoil with fast, anisotropic velocity distributions, consistent with prompt C–X bond fission following excitation via a transition whose dipole moment is aligned parallel to the breaking bond. Upon tuning to shorter wavelengths, this fast component fades and is progressively replaced by a slower, isotropic recoil distribution. Complementary electronic structure calculations provide a plausible explanation for this switch in fragmentation behaviour—namely, the opening of a rival C–S bond extension pathway to a region of conical intersection with the ground state potential energy surface. The resulting ground state molecules are formed with more than sufficient internal energy to sample the configuration space associated with several parent isomers and to dissociate to yield X atom products in tandem with both cyclic and ring-opened partner fragments.

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“…41 It consists of three vacuum chambers for supersonic jet creation, photolysis and ionization, and a field free drift region with the velocity analyzer. The gas mixture is expanded through a pulsed nozzle (General Valve No.…”

Section: Apparatusmentioning

confidence: 99%

Photodissociation dynamics of tert-butylnitrite following excitation to the S1 and S2 states. A study by velocity-map ion-imaging and 3D-REMPI spectroscopy

Wenge

Schmaunz

Kensy

et al. 2012

Phys. Chem. Chem. Phys.

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Excitation of tert-butylnitrite into the first and second UV absorption bands leads to efficient dissociation into the fragment radicals NO and tert-butoxy in their electronic ground states 2 P and 2 E, respectively. Velocity distributions and angular anisotropies for the NO fragment in several hundred rotational and vibrational quantum states were obtained by velocity-map imaging and the recently developed 3D-REMPI method. Excitation into the well resolved vibronic progression bands (k = 0, 1, 2) of the NO stretch mode in the S 1 ' S 0 transition produces NO fragments mostly in the vibrational state with v = k, with smaller fractions in v = k À 1 and v = k À 2. It is concluded that dissociation occurs on the purely repulsive PES of S 1 without barrier. All velocity distributions from photolysis via the S 1 (np*) state are monomodal and show high negative anisotropy (b E À1). The rotational distributions peak near j = 30.5 irrespective of the vibronic state S 1 (k) excited and the vibrational state v of the NO fragment. On average 46% of the excess energy is converted to kinetic energy, 23% and 31% remain as internal energy in the NO fragment and the t-BuO radical, respectively. Photolysis via excitation into the S 2 ' S 0 transition at 227 nm yields NO fragments with about equal populations in v = 0 and v = 1. The rotational distributions have a single maximum near j = 59.5. The velocity distributions are monomodal with positive anisotropy b E 0.8. The average fractions of the excess energy distributed into translation, internal energy of NO, and internal energy of t-BuO are 39%, 23%, and 38%, respectively. In all cases B8500 cm À1 of energy remain in the internal degrees of freedom of the t-BuO fragment. This is mostly assigned to rotational energy. An ab initio calculation of the dynamic reaction path shows that not only the NO fragment but also the t-BuO fragment gain large angular momentum during dissociation on the purely repulsive potential energy surface of S 2 .

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Velocity-map ion-imaging of the NO fragment from the UV-photodissociation of nitrosobenzene

Cited by 19 publications

References 49 publications

The photodissociation dynamics of N-nitrosopyrrolidine from the first and second excited singlet states studied by velocity map imaging

The photodissociation dynamics of N-nitrosopyrrolidine from the first and second excited singlet states studied by velocity map imaging

Near ultraviolet photochemistry of 2-bromo- and 2-iodothiophene: Revealing photoinduced ring opening in the gas phase?

Photodissociation dynamics of tert-butylnitrite following excitation to the S1 and S2 states. A study by velocity-map ion-imaging and 3D-REMPI spectroscopy

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