FLUORESCENCE EFFICIENCY OF CYCLOPENTANONE VAPOR AND ITS RELATION TO PHOTOLYSIS

1963 ◽  
Vol 41 (2) ◽  
pp. 287-292 ◽  
Author(s):  
S. R. La Paglia ◽  
B. C. Roquitte
Keyword(s):  
Fluorescence Spectrum ◽  
High Pressures ◽  
Vibrational Energy ◽  
Energy Content ◽  
Excited Molecule ◽  
Inert Gases ◽  
Fluorescence Efficiency ◽  
Liquid Solutions ◽  
Temperature And Pressure ◽  
First Time

Cyclopentanone vapor, when excited by light of wavelength 3130 Å, gives rise to four different photoproducts and fluorescence. The photochemistry of the molecule has been investigated by Srinivasan (J. Am. Chem. Soc. 81, 1546 (1959); 83, 4344, 4348 (1961)). In the present work the fluorescence spectrum and fluorescence efficiency of cyclopentanone vapor are reported for the first time. The fluorescence spectrum is identical with that obtained from liquid solutions of cyclopentanone, with a maximum at 4100 Å. Time, temperature, oxygen, and inert gases do not affect the spectrum, which contains no component ascribable to phosphorescence, maximum 4450 Å. Beer's law is obeyed.The fluorescence efficiency is also found to be independent of the variables temperature and pressure of inert gas, cyclopentanone, and oxygen. This is in marked contrast with the behavior of the photochemical yields (see work by Srinivasan). The yields of cyclobutane and ethylene tend to increase at high vibrational energy content of the excited molecule (low pressure, high temperature, short exciting wavelengths), while the yield of pentenal increases under conditions of decreasing vibrational energy content (high pressures, etc.). The fact that fluorescence stabilization does not occur in cyclopentanone can be related to the results of photolysis.

Fluorescence Spectrum of 2-Trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone

2007 ◽  
Vol 61 (8) ◽  
pp. 903-907 ◽  
Author(s):  
Jonas P. R. Gustavsson ◽  
Corin Segal
Keyword(s):  
Thermal Stability ◽  
Fluorescence Spectrum ◽  
Measurement Techniques ◽  
Spectroscopic Properties ◽  
Spectroscopic Measurement ◽  
Fluorescence Efficiency ◽  
Wide Range ◽  
Temperature And Pressure ◽  
Nm Range

A perfluorinated ketone, 2-trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone, has been investigated to determine several physical and spectroscopic properties. It was found to exhibit fluorescence similar to that of acetone, emitting over the 360–550 nm range with a peak near 420 nm when excited at 355 nm. This compound's emission is nearly unaffected over a wide range of temperature and pressure in an argon bath gas. Its fluorescence efficiency was found to be three times higher than that of acetone. Combined with low reactivity and thermal stability up to 500 8C, this makes the material an excellent tracer for spectroscopic measurement techniques.

MULTISTAGE DEACTIVATION IN THE PHOTOLYSIS OF HEXAFLUOROACETONE

1964 ◽  
Vol 42 (6) ◽  
pp. 1345-1354 ◽  
Author(s):  
A. N. Strachan ◽  
R. K. Boyd ◽  
K. O. Kutschke
Keyword(s):  
Vibrational Energy ◽  
Excited Molecule ◽  
Single Step ◽  
Inert Gases ◽  
Ultraviolet Region ◽  
Vibrationally Excited ◽  
Vibrational Levels ◽  
New Treatments ◽  
Lower Group ◽  
Vibrational Equilibrium

In principle the vibrationally excited molecule in an upper electronic state, formed by absorption in the ultraviolet region of the spectrum, can attain vibrational equilibrium by two mechanisms. In most discussions of this degradation of vibrational energy it has been considered that the data are represented adequately by a single-step deactivation from high to low vibrational levels rather than by a multistep cascade from one group of vibrational levels to the next lower group. The present work suggests new treatments of the experimental data by which it is possible to distinguish between the single- and the multi-step deactivation processes. It is demonstrated that the literature data on the quantum yield for the decomposition of hexafluoroacetone is better interpreted in terms of a multistep deactivation. Some new data are presented which support this conclusion.Methods to evaluate the efficiencies as deactivating agents of added inert gases are discussed. It is suggested that the deactivation of excited hexafluoroacetone by hydrocarbons might involve chemical rather than, or in addition to, purely physical quenching.

Simultaneous Spectral Imaging of C2*/CH* at Low-to-High Pressure Combustion

2017 ◽  
Author(s):  
Jonathan Reyes ◽  
Kareem Ahmed
Keyword(s):  
Intensity Ratio ◽  
High Pressures ◽  
Diffusion Flames ◽  
Laminar Flames ◽  
Great Promise ◽  
Fuel Distribution ◽  
Premixed Laminar ◽  
The Cost ◽  
Indexing Technique ◽  
First Time

This paper presents the correlation of the intensity ratio of the C2* and CH* radicals to fuel-air measurements over a range of pressures using 93% octane gasoline as the fuel. The measurements are conducted for the first time at high pressures. The study utilizes beam splitting technology to simultaneously view C2* and CH* as a line of sight, global measurement at the cost of resolution. A heavily instrumented constant volume combustor, with optical access, was employed to acquire the data. The ratio of C2* and CH* has been proven to be a good index of the equivalence ratio of premixed laminar flames. This index is attained, quite simply, by filtering each at their respected emissive peaks and taking the ratio of C2* over CH*. This technique shows great promise for use in turbomachinery as it will allow for identification of rich and lean locations in a combustor. By knowing the fuel-air field, combustor inefficiencies can be addressed to allow for greater energy release in combustion. The issue lies with the application of the indexing technique. Presented data to date has been performed on laboratory based diffusion flames exhausting to atmosphere, or premixed, steady, combustor type flames at low pressure (1atm) conditions. These types of flames are not relevant for engine combustor conditions. Understanding the fuel distribution at relevant regimes will reveal where inefficiencies may lie in injector or combustor design. Propagating flame kernels pose a problem in that they do not produce as much light as a steady flame, this makes spectral data difficult to obtain. Steady flames also do not address the effects that pressure may have on the index of C2* and CH*. The authors of this work seek to address three main issues associated with the indexing technique: The feasibility of its application to combustors (hardware design), The ability to operate at low-light ignition events, and the effects pressure may have on the correlation of intensity ratio to the fuel-air measurement.

An improved equation of state for inert gases at high pressures

1980 ◽  
Vol 95 (3) ◽  
pp. 239-252 ◽  
Author(s):  
I.R. Brearley ◽  
D.A. MacInnes
Keyword(s):  
Equation Of State ◽  
High Pressures ◽  
Inert Gases

Thermodynamic Properties of CaSiO3 Perovskite at High Pressure and High Temperature

2009 ◽  
Vol 64 (5-6) ◽  
pp. 399-404 ◽  
Author(s):  
Zi-Jiang Liu ◽  
Xiao-Ming Tan ◽  
Yuan Guo ◽  
Xiao-Ping Zheng ◽  
Wen-Zhao Wu
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
Casio3 Perovskite ◽  
First Time

The thermodynamic properties of tetragonal CaSiO3 perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines the ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state is in excellent agreement with the observed values at ambient condition. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

scholarly journals A theory of the combustion of hydrocarbons

1935 ◽  
Vol 150 (869) ◽  
pp. 36-57 ◽  
Keyword(s):  
Induction Period ◽  
Kinetic Data ◽  
Analytical Data ◽  
Inert Gases ◽  
Original Form ◽  
Comprehensive Theory ◽  
Slow Combustion ◽  
Chain Character ◽  
Energy Chain ◽  
First Time

A comprehensive theory of the combustion of hydrocarbons must describe in detail all the analytic and kinetic data. Up to the present no such theory has been proposed, for though the hydroxylation theory of Bone and his school has been very successful in the former field, it is inadequate in its original form to take account of the latter. In the present paper it is shown that a comparatively small modification, involving the introduction of the conception of chain propagation by free radicals, remedies the earlier deficiency and makes possible for the first time a detailed description of the widely varied phenomena of combustion. The work of Egerton, Hinshelwood, Haber, Semenoff and others has led to the recognition that both rapid and slow combustion are autocatalytic in character, the reaction being propagated through the gas from certain initial centres, so that from every centre started by the primary mechanism, a great many molecules of hydrocarbon are oxidized. The first attempt to interpret the chain character in terms of a concrete theory is embodied in the suggestion of Egerton who has extended the peroxidation theory of Callendar to include an energy-chain mechanism by way of which reactivity is handed on from the active products (peroxides) to new reactant molecules. This theory and its various modifications, however, is unsatisfactory in more than one kinetic aspect, the effect of inert gases in particular being the reverse of the deactivation to be expected for an “energy” chain. Moreover, the peroxidation theory is not reconcilable in all respects with the analytical data, for while the induction period has been interpreted as a period of peroxide building no evidence of any such peroxide formation at this stage has been established, nor is the induction period affected by the addition of any such bodies. There thus arises the need of some further attempt to bring the analytic and kinetic data into relation with one another and in the hypothesis developed below, which we shall call the “atomic chain hypothesis,” it is believed that we have a simple explana­tion which encompasses both the analytical and kinetic results in an adequate manner.

scholarly journals Gaseous combustion at high pressures. Part IV.—The influence of varying initial pressures upon the rate of pressure development and the activation of nitrogen in carbon monoxide-air explosions

1924 ◽  
Vol 105 (732) ◽  
pp. 406-433
Keyword(s):  
Carbon Monoxide ◽  
High Pressures ◽  
Vibrational Energy ◽  
Initial Pressure ◽  
Maximum Pressure ◽  
Time Interval ◽  
Pressure Development ◽  
The One ◽  
Air Explosion ◽  
Energy Absorbing

In the previous paper of this series it was shown :— (1) that when nitrogen is added as a diluent to a mixture of 2CO+O 2 undergoing combustion in a bomb at an initial pressure of 50 atmospheres, it exerts a peculiar energy-absorbing influence upon the system, far beyond that of other diatomic gases, or of argon; (2) that by virtue of such influence, it retards the attainment of maximum pressure in a much greater degree than can be accounted for on the supposition of its acting merely as a diatomic diluent; (3) that the energy so absorbed by the nitrogen during the combustion period, which extends right up to the attainment of maximum pressure, is slowly liberated thereafter as the system cools down ; and that consequently the rate of cooling is greatly retarded for a considerable time interval after the attainment of maximum pressure; (4) that there is no such energy-absorbing effect ( i. e ., other than a purely "diluent" one) when nitrogen is present in a 2H 2 +O 2 mixture similarly undergoing combustion ; but that, on the contrary, the presence of hydrogen in a CO-air mixture undergoing combustion at such high pressures so strongly counteracts the said " energy-absorbing " influence of the nitrogen, that it must be excluded as far as possible from the system before any large nitrogen-effect can be observed. These facts were explained on the supposition that there is some constitutional correspondence between CO and N 2 molecules (whose densities are identical) whereby the vibrational energy (radiation) emitted when the one burns is of such a quality as can be readily absorbed by the other, the two thus acting in resonance. It was further supposed that, in consequence of such resonance, nitrogen becomes chemically " activated " when present during the combustion of carbon monoxide at such high pressures ; and in conformity with this supposition, it was shown that such "activated" nitrogen is able to combine with oxygen more readily than does nitrogen which has merely been raised to a correspondingly high temperature in a hydrogen-air explosion.

THERMODYNAMIC PROPERTIES OF MgSiO3 POST-PEROVSKITE

2010 ◽  
Vol 24 (03) ◽  
pp. 315-324
Author(s):  
ZI-JIANG LIU ◽  
XIAO-WEI SUN ◽  
CAI-RONG ZHANG ◽  
LI-NA TIAN ◽  
YUAN GUO
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
High Pressures And Temperatures ◽  
First Time

The thermodynamic properties of MgSiO 3 post-perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines with ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state of MgSiO 3 post-perovskite is in excellent agreement with the latest observed values. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion, and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

The photolysis of hexafluoroacetone

1956 ◽  
Vol 234 (1199) ◽  
pp. 476-488 ◽  
Keyword(s):  
Quantum Yield ◽  
Initial Step ◽  
Excited Molecule ◽  
Inert Gases ◽  
Wide Range ◽  
Electronically Excited ◽  
Photolytic Decomposition ◽  
Long Lifetime ◽  
The Stability ◽  
Excellent Source

The photolytic decomposition of hexafluoroacetone has been studied over a wide range of temperatures and pressures using light of wavelength 3130 Å. The initial step involves the production of CF 3 radicals, and the only products are C 2 F 6 and CO. The reaction is an excellent source of CF 3 radicals. The quantum yield diminishes with increasing pressure. A mechanism is suggested involving the participation of an electronically excited molecule of comparatively long lifetime, and the effect of various inert gases on the stability of this species is discussed.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: I. n-BUTANE

1938 ◽  
Vol 16b (5) ◽  
pp. 176-193 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Reaction Rate ◽  
High Pressures ◽  
The Other ◽  
First Order ◽  
Decomposition Reactions ◽  
Temperature And Pressure ◽  
Products Of Reaction ◽  
Kinetics Of ◽  
Good Agreement ◽  
Mechanism Of The Reaction

The kinetics of the thermal decomposition of n-butane has been investigated at pressures from 5 to 60 cm. and temperatures from 513 to 572 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in good agreement with the work of Frey and Hepp, but differ greatly from that of Paul and Marek. The reaction rate falls off strongly with diminishing pressure; this is rather surprising for a molecule as complex as butane. The first order constants in a given run fall rapidly as the reaction progresses. The last two facts suggest that chain processes may be involved.A large number of analyses of the products of reaction have been made at various pressures, temperatures, and stages of the reaction, the method being that of low-temperature fractional distillation. The products are virtually independent of temperature and pressure over the range investigated. The initial products, obtained by extrapolation to zero decomposition, are:—H2, 2.9; CH4, 33.9; C3H6, 33.9; C2H4, 15.2; C2H6, 14.1%. The mechanism of the reaction is discussed, and the results are compared with those of the other paraffin decompositions.

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