Gas-phase chemistry of fluoroimidogen(a1.DELTA.): quenching rate constants

Abstract

The reaction of excess F atoms with HN3 in a halocarbon-coated flow reactor has been used to generate and study the quenching reactions of NF(a*A,y-0) at 300 K. Fifteen reagents, selected to represent a variety of chemical interactions, were tested in order to provide a survey of quenching rate constants that could be compared to 02(a*Ag) and NH(a'A). A range of rate constants was found which varied from ~1.0 X 10"u cm3 s"1 for N(CH3)3 to ~1.0 X 10"15 cm3 s"1 for N2, H2, and NO. The.NF(a'A) molecule is much less reactive than NH(a'A), and it seems to more closely resemble 02(alAg). However, the quenching rate constants for NF(a'A) generally are larger than for 02(a'Ag) and show a greater variation from one reagent to another. The self-quenching rate constant for NF(a'A) is (2.2 ± 1.2) X 10"12 cm3 s~* with energy pooling to give NF(b'S+) being a small component of the total self-quenching reaction.

Dissociation of Cyanogen Azide: An Alternative Route to Synthesis of Carbon Nitride

“…Since this term cannot significantly exceed unity, consistent with the mechanism and observations discussed above, one then finds with t ∼ 1 ms and [NCN] ∼ [initial donor] ∼ 3 × 10 13 /cm 3 that k < 3 × 10 -11 cm 3 /(molecule s). For comparison, the rates of metastable self-annihilation in NF and NCl have been previously measured as approximately 3 × 10 -12 and 3 × 10 -11 cm 3 /(molecule s), respectively. ,, …”

“…For comparison, the rates of metastable self-annihilation in NF and NCl have been previously measured as approximately 3 × 10 -12 and 3 × 10 -11 cm 3 /(molecule s), respectively. 6,7,61 At low levels of donor injection, the initial rise of CN(B-X) chemiluminescence tracks the rate of parent molecule dissociation. The rise of CN(B) was spatially resolved by varying injector probe position in relation to a fixed observation zone, and these data were found to approximately correlate with corresponding variations of film thickness.…”

Collisional Quenching of NCl(a1.DELTA.,v=0) and the Chain Decomposition of ClN3

“…The slow quenching of o~( a~A . 4 is understandable in the sense that it can engage only in "physical" E to V energy transfer processes with these diatomics. The difference between the rates for NCl(alA) and NF(alA) seems to be too large to attribute solely to increased spin-orbit coupling in the chloride.…”

“…NCl(a'A,y=0) + 02(X32g") -NC1(X32") + 02(a'Ag) (4) Indirect indications of the presence of (^(a'Ag) in Clyne's experiments suggested the occurrence of this process, which is fully allowed by conservation of both spin and orbital angular momentum. The process as written in eq 4 is nonresonant, with an exothermicity near 1400 cm'1.…”

“…Production of (^(a'Ag) by reaction 4 is particularly interesting in the context of the possible chain decomposition of C1N3 as in eqs 1 and 2. Like N2(u), 02(a1Ag) metastables carry sufficient energy to dissociate C1N3, and a chain carried by both species can be envisioned: C1N3 + hv -NCl(a'A) + 2(») (1) NCl(a'A) + 02(X32") -NC1(X32") + 02(alAg) (4) 02(a'Ag) + C1N3 -02(X32g") + NCl(a'A) + N2(uO (5) N2(t>0 + C1N3 -N2(p,0 + NCl(a'A) + N2(»0 (2) At the steady state of this chain, both NCl(a'A) and 02(a'Ag) would be present, in amounts governed by the rates of reactions 4 and 5. We have obtained evidence of the operation of this chain from experiments in which the NCl(a'A)/02 energy transfer process is observed with higher initial C1N3 densities photolyzed at 249 nm.…”