Pressure Dependence of Energy Transfer from Pyrene to Perylene

1972 ◽  
Vol 57 (4) ◽  
pp. 1473-1475 ◽  
Author(s):  
P. C. Johnson ◽  
H. W. Offen
Keyword(s):  
Energy Transfer ◽  
Pressure Dependence

Mechanism and Models for Collisional Energy Transfer in Highly Excited Large Polyatomic Molecules

1995 ◽  
Vol 48 (11) ◽  
pp. 1787 ◽  
Author(s):  
RG Gilbert
Keyword(s):  
Energy Transfer ◽  
Pressure Dependence ◽  
Energy Flow ◽  
Functional Form ◽  
Average Energy ◽  
Theoretical Understanding ◽  
Point Energy ◽  
Collisional Energy ◽  
Collisional Energy Transfer ◽  
Recombination Reactions

Collisional energy transfer in highly excited molecules (say, 200-500 kJ mol-1 above the zero-point energy of reactant, or of product, for a recombination reaction) is reviewed. An understanding of this energy transfer is important in predicting and interpreting the pressure dependence of gas-phase rate coefficients for unimolecular and recombination reactions. For many years it was thought that this pressure dependence could be calculated from a single energy-transfer quantity, such as the average energy transferred per collision. However, the discovery of 'supercollisions' (a small but significant fraction of collisions which transfer abnormally large amounts of energy) means that this simplistic approach needs some revision. The 'ordinary' (non-super) component of the distribution function for collisional energy transfer can be quantified either by empirical models (e.g., an exponential-down functional form) or by models with a physical basis, such as biased random walk (applicable to monatomic or diatomic collision partners) or ergodic (for polyatomic collision partners) treatments. The latter two models enable approximate expressions for the average energy transfer to be estimated from readily available molecular parameters. Rotational energy transfer, important for finding the pressure dependence for recombination reactions, can for these purposes usually be taken as transferring sufficient energy so that the explicit functional form is not required to predict the pressure dependence. The mechanism of 'ordinary' energy transfer seems to be dominated by low-frequency modes of the substrate, whereby there is sufficient time during a vibrational period for significant energy flow between the collision partners. Supercollisions may involve sudden energy flow as an outer atom of the substrate is squashed between the substrate and the bath gas, and then is moved away from the interaction by large-amplitude motion such as a ring vibration or a rotation; improved experimental and theoretical understanding of this phenomenon is seen as an important area for future development.

scholarly journals Experimental Observations of the Diffusion Cooling of Electrons in Argon

1975 ◽  
Vol 28 (6) ◽  
pp. 675 ◽  
Author(s):  
T Rhymes ◽  
RW Crompton
Keyword(s):  
Diffusion Coefficient ◽  
Energy Transfer ◽  
Satisfactory Agreement ◽  
Pressure Dependence ◽  
Pressure Range ◽  
Sampling Technique ◽  
Cooling Effect ◽  
Hydrogen Mixtures ◽  
Gas Molecules

The cooling by diffusion of electrons in argon and in argon–hydrogen mixtures has been studied by the Cavalieri density sampling technique. In the case of argon, the measured values of the reduced diffusion coefficient ND varied by more than a factor of two over the pressure range 2–8 kPa. When small quantities of hydrogen were added to the argon, the cooling effect was reduced due to the increased energy transfer between the electrons and gas molecules. For argon, the magnitude and pressure dependence of ND are in satisfactory agreement with the recent calculations by Leemon and Kumar (1975).

Primary Processes in the Vacuum Ultraviolet Photolysis of Ethyl Fluoride at 147 nm

1972 ◽  
Vol 50 (10) ◽  
pp. 1443-1447 ◽  
Author(s):  
S. C. Chan ◽  
Y. Inel ◽  
E. Tschuikow-Roux
Keyword(s):  
Energy Transfer ◽  
Pressure Dependence ◽  
Room Temperature ◽  
Vacuum Ultraviolet ◽  
Photochemical Reactions ◽  
Energy Transfer Efficiency ◽  
Gas Pressure ◽  
Inert Gas ◽  
Ultraviolet Photolysis ◽  
Ethyl Fluoride

The photolysis of C2H5F at 147 nm was studied at room temperature. The principal products include C2H3F, C2H2, C2H4, CH4, and C2H6. The principal primary photochemical reactions involve the molecular elimination of HF and H2, and, to a lesser extent, C—F and C—C bond fission. The effect of reactant and added inert gas pressure on the product yields has been investigated and it was found that the stabilization/decomposition ratio, C2H4/C2H2, displays opposite pressure dependence with ethyl fluoride and argon. This result is interpreted in terms of the higher energy transfer efficiency of the C2H5F molecule.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

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