Photolysis of Nitromethane in Gas Phase at 313 nm

Honda, Koichi; Mikuni, Hitoshi; Takahasi, Makoto

doi:10.1246/bcsj.45.3534

Cited by 34 publications

(12 citation statements)

References 23 publications

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“…This state correlates asymptotically with the ground-state singlet, yielding the CH 3 and NO 2 radicals. Despite the claim that the electronic transition plays an important role in the gas-phase photolysis of nitromethane, , spectroscopic parameters have not been identified for the triplet state. A recent DFT comparative study 27 provided only three structural parameters: R (C−N), R (N−O), and the ∠CNO.…”

Section: Resultsmentioning

confidence: 99%

“…The authors have concluded that the transition plays an important role in the gas-phase photolysis of nitromethane, supporting an earlier claim that photolysis leading to CH 3 and NO 2 occurs via a triplet intermediate. 25 The role of a nonradiative deexcitation channel from the excited to the ground state has also been observed, 26 suggesting the need for a further characterization of the excited states of this molecule.…”

Section: Introductionmentioning

confidence: 99%

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DFT and ab Initio Study of the Unimolecular Decomposition of the Lowest Singlet and Triplet States of Nitromethane

Manaa

Fried

1998

J. Phys. Chem. A

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The fully optimized potential energy curves for the unimolecular decomposition of the lowest singlet and triplet states of nitromethane through the C−NO2 bond dissociation pathway are calculated using various DFT and high-level ab initio electronic structure methods. We perform gradient corrected density functional theory (DFT) and multiconfiguration self-consistent field (MCSCF) to conclusively demonstrate that the triplet state of nitromethane is bound. The adiabatic curve of this state exhibits a 33 kcal/mol energy barrier as determined at the MCSCF level. DFT methods locate this barrier at a shorter C−N bond distance with 12−16 kcal/mol lower energy than does MCSCF. In addition to MCSCF and DFT, quadratic configuration interactions with single and double substitutions (QCISD) calculations are also performed for the singlet curve. The potential energy profiles of this state predicted by DFT methods based on Becke's 1988 exchange functional differ by as much as 17 kcal/mol from the predictions of MCSCF and QCISD in the vicinity of the equilibrium structure. The computational methods predict bond dissociation energies 5−9 kcal/mol lower than the experimental value. DFT techniques based on Becke's 3-parameter exchange functional show the best overall agreement with the higher level methods.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

DFT and ab Initio Study of the Unimolecular Decomposition of the Lowest Singlet and Triplet States of Nitromethane

Manaa

Fried

1998

J. Phys. Chem. A

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“…The photochemistry of nitromethane (CH 3 NO 2 ) has been extensively studied for many years − principally because the molecule is an important prototypical energetic material. Its ultraviolet absorption spectrum consists of two bands: a weak band around 270 nm with very little absorption strength at wavelengths longer than 350 nm and a very much stronger band at about 198 nm .…”

Section: Introductionmentioning

confidence: 99%

“…There is conflicting evidence of relatively minor competing dissociation channels for nitromethane using a Kr flash photolysis lamp 1 and a mercury arc lamp at 313 nm Kwok et al .…”

Section: Introductionmentioning

confidence: 99%

Multiphoton Ionization and Dissociation of Nitromethane Using Femtosecond Laser Pulses at 375 and 750 nm

et al. 1997

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The photochemistry of nitromethane has been studied extensively for many years. Although it is generally agreed that the principal photodissociative process is cleavage of the C−N bond to yield the methyl radical and nitrogen dioxide, there is some evidence of minor competing dissociation channels. A number of different groups have used lasers of different wavelengths, but the results of these studies vary considerably and no clear picture of the minor dissociative channels has yet emerged. The use of femtosecond (fs) duration laser pulses for photoionization of molecules is currently an area of considerable interest, since the process can lead to the efficient production of intact molecular ions. It was felt that femtosecond laser mass spectrometry (FLMS) could provide added information on the dissociation pathways of nitromethane. Laser pulses of 90 fs time duration at wavelengths of 375 and 750 nm, coupled to a time-of-flight mass spectrometer, have been used in this study, and contrary to photoexcitation using nanosecond (ns) pulses, a large parent ion, 61 (CH3NO2 +), is detected together with strong peaks at m/e = 15 (CH3 +), 30 (NO+), 46 (NO2 +) as well as a number of other minor peaks. This fragmentation pattern can be explained by a predominantly ID (ionization followed by dissociation) route.

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“…lysis have been interpreted to support the scission of the C-N bond as the main primary process (15).…”

Section: Jmentioning

confidence: 92%

High Power Picosecond Photolysis of Simple Organic Molecular Gases

Craig

Faust

Goldberg

et al. 1981

Fast Reactions in Energetic Systems

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High-power picosecond UV pulses from a Nd:YAG modelocked laser were used to induce a visible emission from a variety of gaseous organic molecules.We report the observation of electronically excited C', CH, CN and H fragments. The spectral characteristics and :im development of the emitting species are highly dependent ( j uoon the structure of the parent molecules., cLaser Dhotolsis of simple molecules has contributed to a deeper understanding of dynamical processes in photodissociation. &N Our :oncern in the present work is with the decomoosition of sim-:ie compounds which afford generic models of processes important in explosives, fuels and other energetic materials.Multiphoton IR and JV laser dissociation (L-4) has previously been applied to study the primary decomposition processes of gas-phase hydrocarbons and subsequent reaction of fragments having significance in the kinetics or combustion. These experiments have been performed in the nanosecond time domain and at millitorr gas pressures in order to maintain a collision-free time regime during the duration of the exci:ation pulse.In our experiments the time resolution afforded by oicosecond pulse excitation enables such photoivsis even at atmospheric pressures, yielding high fragment concentrations. For the pressures and high flux densities employed in this work, multiohoton absorption processes can be accompanied by dielectric ireakdown (5).ndeed, since laser-induced breakdown is a nonresonant process, this very non-specificity facilitates the decomposition of a wide variety of materials.Here, we demonstrate the utility of the technique in generating :ragmencs w . se emission spectra reflect their orecursors.We .ave carried Out the pno:olvsis :f ketene, methane, carbon moncxioe L and ni-romechane at ressures in the range of 10-500 torr, and _s:ue'd the l'uminescence from 2, CH, CN and H fragments.

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Photolysis of Nitromethane in Gas Phase at 313 nm

Cited by 34 publications

References 23 publications

DFT and ab Initio Study of the Unimolecular Decomposition of the Lowest Singlet and Triplet States of Nitromethane

DFT and ab Initio Study of the Unimolecular Decomposition of the Lowest Singlet and Triplet States of Nitromethane

Multiphoton Ionization and Dissociation of Nitromethane Using Femtosecond Laser Pulses at 375 and 750 nm

High Power Picosecond Photolysis of Simple Organic Molecular Gases

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