“…At the densities of the pulsed experiments, considerable radiation trapping is expected for the V ) 1 f V ) 0 transition in this molecule. This phenomenon is well-known for CO 2 , and k 14 was determined by multiplying the reported 16 radiation-trapped rate for CO 2 by the factor of 4.8 noted above. The flow reactor experiments described above indicate that N 2 (V) quenching is very slow, even on Pyrex walls.…”
A number of experiments have been performed in an effort to better understand the photoinitiated chain
decomposition of ClN3. Discharge-flow methods were used to determine the rate of energy exchange between
vibrationally excited N2 (a likely chain carrier) and ClN3. The rate constant for energy transfer from N2(v=1)
to ClN3 was found to be (2.0 ± 1.0) × 10-13 cm3 s-1 at 300 K. This process is thought to excite the ν2 mode
in ClN3 with the release of 281 cm-1 of excess energy. Experiments were also performed in which the
decomposition of ClN3 was initiated by photolysis with a pulsed KrF laser at 249 nm, with subsequent
observation of the time dependence of the densities of ClN3, electronically excited NCl(aΔ), and vibrationally
excited ClN3(ν2). A kinetic model for the ClN3 decomposition was assembled based on reactions with NCl(a1Δ) and N2(ν).
“…At the densities of the pulsed experiments, considerable radiation trapping is expected for the V ) 1 f V ) 0 transition in this molecule. This phenomenon is well-known for CO 2 , and k 14 was determined by multiplying the reported 16 radiation-trapped rate for CO 2 by the factor of 4.8 noted above. The flow reactor experiments described above indicate that N 2 (V) quenching is very slow, even on Pyrex walls.…”
A number of experiments have been performed in an effort to better understand the photoinitiated chain
decomposition of ClN3. Discharge-flow methods were used to determine the rate of energy exchange between
vibrationally excited N2 (a likely chain carrier) and ClN3. The rate constant for energy transfer from N2(v=1)
to ClN3 was found to be (2.0 ± 1.0) × 10-13 cm3 s-1 at 300 K. This process is thought to excite the ν2 mode
in ClN3 with the release of 281 cm-1 of excess energy. Experiments were also performed in which the
decomposition of ClN3 was initiated by photolysis with a pulsed KrF laser at 249 nm, with subsequent
observation of the time dependence of the densities of ClN3, electronically excited NCl(aΔ), and vibrationally
excited ClN3(ν2). A kinetic model for the ClN3 decomposition was assembled based on reactions with NCl(a1Δ) and N2(ν).
“…The biacetyl formed via this pathway is designated k2 ; below it is shown that biacetyl (designated k1 ) is also formed via another pathway. The oxidation of acetyl radicals has been considered recently by several groups, ,− and the atmospheric oxidation of most of the other organic species is moderately well understood. ,− 3 Reaction Mechanism for But-2-yne + HO in the Presence of O 2 • Reaction Channels Originating from e2 4 Glyoxal Formation from the Self-Reaction of Peroxyl Radical E2 …”
Section: Reaction Mechanismsmentioning
confidence: 99%
“…The biacetyl formed via this pathway is designated k2; below it is shown that biacetyl (designated k1) is also formed via another pathway. The oxidation of acetyl radicals has been considered recently by several groups, 23,[28][29][30] and the atmospheric oxidation of most of the other organic species is moderately well understood. 1,[25][26][27]…”
The aim of this study is to improve understanding of the tropospheric oxidation of ethyne (acetylene, C2H2) and but-2-yne, which takes place in the presence of HO and O2. The details of the potential energy hypersurface have been discussed in a previous article [Maranzana et al., J. Phys. Chem. A 2008, 112, XXXX]. For both molecules, the initial addition of HO radical to the triple bond is followed by addition of O2 to form peroxyl radicals. In both reaction systems, the peroxyl radicals take two isomeric forms, E1 and E2 for ethyne and e1 and e2 for but-2-yne. Energy transfer parameters (alpha = 250 cm-1) for the ethyne system were obtained by simulating laboratory data for N2 buffer gas, where O2 was not present. In simulations of C2H2 + HO when O2 is present, E1 reacts completely and E2 reacts almost completely, before thermalization. Radical E1 produces formic acid ( approximately 44%) and E2 gives glyoxal ( approximately 53%), in quite good agreement with experiments. For but-2-yne, pressure-dependent laboratory data are too scarce to obtain energy transfer parameters directly, so simulations were carried out for a range of values: alpha = 200-900 cm-1. Excellent agreement with the available experimental yields at atmospheric pressure was obtained with alpha = 900 cm-1. Two reaction channels are responsible for acetic acid formation, but one is clearly dominant. Biacetyl is produced by reactions of e1 and, to a minor extent, e2. The peroxyl radical e2 leads to less than 8% of all products. Vinoxyl radical (which has been reported in experiments involving C2H2 + HO) and products of its reactions are predicted to be negligible under atmospheric conditions.
“…They make an important comparative pair because they are isoelectronic, have the same mass, and have similar vibrational frequencies. CO 2 has long been used in this role (see, for example, refs [1][2][3][4][5][6][7][8][9][10][11][12], but the studies of N 2 O began much more recently and are far less extensive. [13][14][15][16][17][18][19][20][21][22][23][24][25] Most experimental measurements have been confined to deactivation of both CO 2 and N 2 O excited to the (00 0 1) vibrational level of the asymmetric stretch mode, ν 3 .…”
The time-resolved infrared fluorescence (IRF) technique has been used to study the vibrational deactivation of CO 2 (00 0 1) and N 2 O(00 0 1) by C 6 D 5 CH 3 and C 6 H 5 CD 3 at ambient temperature (295 ( 2 K). The bimolecular deactivation rate constants were found to be (242 ( 17) × 10 3 and (145 ( 5) × 10 3 Torr -1 s -1 , respectively, for the deactivation of CO 2 (00 0 1), and (253 ( 13) × 10 3 and (376 ( 20) × 10 3 Torr -1 s -1 , respectively, for the deactivation of N 2 O(00 0 1). Experimental deactivation probabilities are calculated and compared with our previous data for deactivation of the same two excited molecules by the colliders C 6
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