Velocity Map Imaging Study of the Photodissociation of CH<sub>3</sub>SH: Internal Energy Distribution of the SH Fragment

Izquierdo, J. G.; Amaral, G. A.; Ausfelder, Florian; Aoiz, F. J.; Bañares, Luis

doi:10.1002/cphc.200600232

Cited by 10 publications

(17 citation statements)

References 25 publications

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“…In a recent publication 14 we have studied the CH 3 fragments from the photolysis of CH 3 SH at 205 nm ͑second absorption band͒ with the velocity map imaging technique and observed an inverted SH vibrational population consistent with the theoretical predictions. In the present paper, we explore the extent to which the energy is channeled into the SH product vibration due to the geometric changes occurring in the region of the intersection as a function of excitation energy and the differences with the previously unobserved SH nascent vibrational energy arising from the adiabatic photodissociation on the 1 1 AЉ surface.…”

Section: Introductionsupporting

confidence: 68%

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Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X̃A12)+SH(XΠ2) channel

Amaral

Ausfelder

Izquierdo

et al. 2007

The Journal of Chemical Physics

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The CH3(X2A1)+SH(X2Pi) channel of the photodissociation of CH3SH has been investigated at several wavelengths in the first 1 1A"<--X 1A' and second 2 1A"<--X1A' absorption bands by means of velocity map imaging of the CH3 fragment. A fast highly anisotropic (beta=-1+/-0.1) CH3(X2A1) signal has been observed in the images at all the photolysis wavelengths studied, which is consistent with a direct dissociation process from an electronically excited state by cleavage of the C-S bond in the parent molecule. From the analysis of the CH3 images, vibrational populations of the SH(X2Pi) counterfragment have been extracted. In the second absorption band, the SH fragment is formed with an inverted vibrational distribution as a consequence of the forces acting in the crossing from the bound 2 1A" second excited state to the unbound 1 1A" first excited state. The internal energy of the SH radical increases as the photolysis wavelength decreases. In the case of photodissociation via the first excited state, the direct production of CH3 leaves the SH counterfragment with little internal excitation. Moreover, at the longer photolysis wavelengths corresponding to excitation to the 1 1A" state, a slower anisotropic CH3 channel has been observed (beta=-0.8+/-0.1) consistent with a two step photodissociation process, where the first step corresponds to the production of CH3S(X2E) radicals via cleavage of the S-H bond in CH3SH, followed by photodissociation of the nascent CH3S radicals yielding CH3(X2A1)+S(X3P0,1,2).

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Section: Introductionsupporting

confidence: 68%

“…The experimental setup has been described previously, 14 and only a brief account of the standard procedure will be given here. The whole experiment runs at a repetition rate of 10 Hz.…”

Section: Methodsmentioning

confidence: 99%

Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X̃A12)+SH(XΠ2) channel

Amaral

Ausfelder

Izquierdo

et al. 2007

The Journal of Chemical Physics

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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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“…The ultraviolet (UV) photodissociation studies of methyl mercaptan (CH 3 SH) have received a great deal of attention in recent years [2][3][4]. The near UV electronic spectrum [5] of CH 3 SH shows two absorption bands.…”

Section: Introductionmentioning

confidence: 99%

Theoretical studies on the spectroscopic properties of methyl mercaptan (CH3SH)

Yang

2015

J Struct Chem

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The properties of the ground and low-lying excited states of methyl mercaptan (CH 3 SH) are studied by using quantum chemistry methods. The geometric parameters and energies of the ground state and the triplet excited state are calculated in this work. It is shown that the calculated geometries of the ground and triplet state are stable and the triplet state potential energy surface has the repulsive feature. The calculated vertical excitation energies and vertical ionization potentials of methyl mercaptan are in best agreement with the experimental values. In addition, the vertical electron affinity and the adiabatic electron affinity of the CH 3 SH molecule are also calculated.

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Velocity Map Imaging Study of the Photodissociation of CH₃SH: Internal Energy Distribution of the SH Fragment

Cited by 10 publications

References 25 publications

Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X̃A12)+SH(XΠ2) channel

Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X̃A12)+SH(XΠ2) channel

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

Theoretical studies on the spectroscopic properties of methyl mercaptan (CH3SH)

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Velocity Map Imaging Study of the Photodissociation of CH3SH: Internal Energy Distribution of the SH Fragment

Cited by 10 publications

References 25 publications

Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X̃A12)+SH(XΠ2) channel

Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X̃A12)+SH(XΠ2) channel

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

Theoretical studies on the spectroscopic properties of methyl mercaptan (CH3SH)

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Velocity Map Imaging Study of the Photodissociation of CH₃SH: Internal Energy Distribution of the SH Fragment