Photodissociation of methylnitrite: State distributions, recoil velocity distribution, and alignment effects of the NO(X 2Π) photofragment

Abstract

The photodissociation of CH3ONO→CH3O+NO at 363.9 nm generates vibrationally, rotationally, and translationally excited fragments (fNOvib =3%, fNOrot =15%, fNOtrans =33%). By means of two-photon LIF and sub-Doppler spectroscopy in combination with various polarization schemes of dissociation and probe lasers, the nascent NO(X 2Π) photofragment was characterized with respect to state distributions and three-dimensional recoil velocity distribution. Furthermore, the rotational alignment and the Λ-state populations were determined. Through the rotational alignment dependence of Doppler profiles probed by differently polarized transitions (R and S), the J–v vector correlation was assessed. Based on these results, stereochemical and dynamical information about the dissociation was obtained which shows that the fragmentation process is planar and takes place within 210 fs.

Photoinduced Bimolecular Reactions in Homogeneous [CH3ONO]nClusters

“…The DEA reflects the orientation of the unpaired pπ electron with respect to the plane of rotation. , Below the high J‘‘ limit, mixing of the Λ-doublet states leads to a reduction of the maximum DEA value (±1), which is indicated by the dotted line in Figure c. The symmetry of the S 1 excited state of methyl nitrite with respect to the molecular plane is A‘‘ so that the previously established planar fragmentation − should lead to a clear propensity for the same symmetry A‘‘ in the NO(X̃ 2 Π) fragment. The observed value of DEA = 0 implies that any vestige of the electronic state of the parent molecule before fragmentation has been lost under cluster conditions.…”

“…for the pyrolysis mechanism of methyl nitrite. However, it is experimentally and theoretically well established that the dissociation of CH 3 ONO on the S 1 surface is very fast in the range of about 200 fs ,,− and that the quantum yield for fragmentation to NO and CH 3 O is one. , Thus S 1 → S 0 internal conversion and hence reaction 6 can be ruled out. (In this context, it is noted that a reaction of electronically excited CH 3 ONO ( S 1 ) with a CH 3 ONO ( S 0 ) cluster molecule, yielding HNO and H 2 CO as reactions products, is energetically not feasible. − )…”

Dissociation Pathways of the CH2CH2ONO Radical: NO2+ Ethene, NO + Oxirane, and a Non-Intrinsic Reaction Coordinate HNO + Vinoxy Pathway

“…Gaseous alkyl nitrites (R–ONO, where R is an alkyl group) are important intermediates in the formation of chemical smog and in the regulation of ozone levels. − Both photolysis and thermal decomposition of these species are rapid; photolysis under ultraviolet light occurs readily via photoabsorption in the nitrite moiety, which has absorption bands near 350 and 200 nm. The atmospheric impact of alkyl nitrite chemistry and photochemistry has motivated studies on nitrous acid (HONO), − methyl nitrite (CH 3 ONO), − and a number of higher nitrites as well. − …”

Photolysis of n-butyl nitrite and isoamyl nitrite at 355 nm: A time-resolved Fourier transform infrared emission spectroscopy and ab initio study

“…2 The primary dissociation pathway associated with the two UV absorption bands was found to be due to the cleavage of the weak RO-NO bond ͑ϳ170 kJ/ mol͒. 8 While extensive studies have been performed on nitrous acid ͑HONO͒, [3][4][5][9][10][11] methyl nitrite ͑CH 3 ONO͒, 6,7,[12][13][14][15] and tert-butyl nitrite ͑͑CH 3 ͒ 3 CONO͒, 7,16-19 there remains quite meager in the photodissociation studies on n-butyl nitrite ͑n-C 4 H 9 ONO͒ and isoamyl nitrite ͑͑CH 3 ͒ 2 C 3 H 5 ONO͒. To the best of our knowledge, only two recent works on the photodissociation dynamics of n-C 4 H 9 ONO were reported by Yue et al, 2,20 who measured the nascent NO ͑Ref.…”