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Title: Some kinetic and spectroscopic studies of nitrous oxide and its ions
Author: Holliday, Michael G.
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1968
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The work in this thesis deals with some aspects of the simple molecule, nitrous oxide. It is convenient to divide the work into four parts: (i) Oxidation of Hydrogen in Nitrous Oxide The reaction, in a static system, was followed by measuring N2O concentration by its absorption at 2200 A. It was found that in the region of 560°C the reastion rate was between 500 and 1000 times as fast as N2O decomposition. The reaction may be considered in two parts; 1) a "high" pressure reaction which occurs at total pressures greater than 100 mm Hg and whose initial rate is given by: Initial rate(mm Hg/min)=1.37+/-0.05x10 15(-62.5+/-2.1/RT).[N2O][H2]0.25 where [N2O] and [H2] represents the pressure of N2O and H2 in mm Hg; 2) a "low" pressure reaction which occurs at total pressures less than 60 mm Hg and whose initial rate is given by: Initial rate (mm Hg/min)=8.26+/-0.30x1013 (-62.5+/-2.1/RT)[N2O]2. The initial catalysis is a result of the chain branching process H+O2 → OH+O and it is suggested that the inhibition is due to the formation of small amounts of nitric oxide (0.2 to 0.3%). An explanation is suggested for the minima in explosion limit vs temperature curves observed by workers investigating the explosive N2O/H2 reaction. A small isotope effect is noticed when hydrogen is replaced by deuterium (kH/KD ≈ 2) which approaches unity at low pressures. (ii) Oxidation of Carbon Monoxide in Nitrous Oxide The N2O/CO reaction at 700°C proceeds at about three times the rate of N2O decomposition. It is accompanied by a blue chemiluminescence and the formation of small amounts of oxygen. The reaction was followed by measuring N2O pressure spectroscopically, the production of oxygen manometrically and the intensity of the chemiluminescence at 4500 A. The reaction is first order in N2O and about 0.3 order in CO and has an activation energy of 59.7 +/- 1.5 kcal. It is suggested that the increase in rate relative to the N2O decomposition is a result of water in 10's p.p.m. quantities initiating H and OH radical propagated reaction chains. (iii) Temperature Dependence of the Absorption of N2O in the Quartz Ultra-Violet. The continuous absorption of nitrous oxide between 1900 and 2800 A has been studied from 20 to 680°Co. The absorption coefficient, at any given wavelength, increases exponentially with temperature leading to apparent activation energies. It is proposed that the continuum is due to transitions from bending vibrationally excited ground state molecules to a bent repulsive upper state. It is suggested that the upper state is a 1A' state correlating with a 1B2 state of the isoelectronic CO2 molecule. A small portion of the upper potential energy curve is derived. (iv) Ion-Molecule Reactions in N2O/H2 System (v) Ion-Molecule Reactions in N2O/H2, HD and D2, and CO2/D2 and HD systems have been studied in a mass spectrometer ion source. It was shown that two concurrent ion-molecule reactions take place in each system. The reactions obey the theoretical linear dependence of phenomenological cross-section on (ion energy)-½ . The reaction cross-sections and bimolecular rate constants for the individual reactions AB+ + X2 ?ABX+ + X X2+ + AB →ABX+ + X where AB = CO2 or N2O and X2 =D2 or HD, were obtained and compared with theory. It was found that the overall reaction cross-sections for CO2/D2 and HD systems (i.e. the sum of both reactions) are in agreement with those predicted by the Gioumousis-Stevenson theory.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available