The high-pressure range of the reaction of CH(2Π) with N2

Abstract

The pressure dependent thermal rate constant of the reaction of CH(2Π) and N2 has been studied from 200 to 715 K at total pressures between 1 and 150 bar of helium. The CH radicals have been generated using multiphoton laser flash photolysis of CHClBr2 or CHBr3 at 248 nm and detected by saturated laser induced fluorescence (SLIF). At 200, 250, 300, 400, and 500 K falloff curves have been constructed and the high pressure limit rate constant has been determined to be k1,∞=(4.1±0.8)10−11 (T/300 K)−0.15 cm3 molecule−1 s−1. At higher temperatures thermal decomposition of the CHN2 adduct has been observed and the equilibrium constant derived by analyzing the concentration decays. By third law analysis the equilibrium constant has been evaluated with a reaction enthalpy ΔH°R (0 K)=−(97±10) kJ mol−1. Our results are compared with recent calculations of the potential energy surface (PES) and other experimental data at low pressures as well as shock tube studies. The high-pressure limiting rate constants are treated in terms of statistical reaction rate theory. A simple kinetic model has been developed to describe the measured rate constants in an extended pressure (10−3–150 bar) and temperature range (200–3500 K).