Low energy electron ranges in liquids: determination by nonhomogeneous kinetics

1977 ◽  
Vol 55 (11) ◽  
pp. 2050-2062 ◽  
Author(s):  
J.-P. Dodelet
Keyword(s):  
Critical Temperature ◽  
Melting Point ◽  
Distribution Functions ◽  
Liquid Density ◽  
Range Distribution ◽  
Total Ionization ◽  
Free Ion ◽  
Drastic Increase ◽  
Pass Through ◽  
Ion Yields

Free ion yields have been measured in four hydrocarbon liquids: n-pentane, cyclopentane, neopentane, and neohexane. Each liquid has been studied from room temperature or below up to the critical temperature. Theoretical curves have been calculated using the relation between the free ion yields and the external field strength derived by Terlecki and Fiutak on the basis of an equation by Onsager. Two popular electron range distribution functions, Gaussian and exponential, have been shown not to be an adequate representation of the reality as far as the model used for the calculations is concerned. In order to fit experimental points, both range distribution functions would require a drastic increase in the total ionization yield, Gtot, with temperature increase. This would mean an unrealistic decrease of the ionization potential of the molecule from the melting point up to the critical temperature.It is possible to keep Gtot quite constant and within the range of values obtained by other techniques by extending the Gaussian range distribution function with a (range)−3 probability tail. The most probable range can be normalized for the liquid density. This parameter has been used to obtain information about the behaviour of epithermal electrons in the four alkane liquids from the melting point up to the critical temperature.(1) Normalized penetration ranges of epithermal electrons are dependent on the structure of the molecule in the entire liquid range but differences are smaller at critical than at low temperatures.(2) Normalized penetration ranges of epithermal electrons pass through a maximum in the liquid phase for neopentane, neohexane, and cyclopentane. No maximum is observed for n-pentane.(3) There is no drastic change in the behaviour of epithermal electrons in these alkanes at the critical temperature.

X-Radiolysis Ion Yields and Electron Ranges in Liquid Xenon, Krypton, and Argon: Effect of Electric Field Strength

1973 ◽  
Vol 51 (5) ◽  
pp. 641-649 ◽  
Author(s):  
Maurice G. Robinson ◽  
Gordon R. Freeman
Keyword(s):  
Field Strength ◽  
Gas Phase ◽  
Electric Fields ◽  
Zero Field ◽  
Energy Effect ◽  
Secondary Electrons ◽  
Total Ionization ◽  
Field Dependent ◽  
Free Ion ◽  
Ion Yields

X-Radiolysis ion yields were measured at electric fields between 1 and 60 kV/cm in argon at 87 °K, krypton at 148 °K, and xenon at 183 °K. The results were analyzed according to a theoretical model to obtain the total ion yields Gtot,the free ion yields at zero field strength Gfi0 and the most probable penetration ranges b of the secondary electrons in the liquids. The respective values were: Ar, 7.3, 2.9, 1330 Å; Kr, 13.0, 5.8, 880 Å; Xe, 13.7, 7.0, 720 Å. The total ionization yields in these substances are greater in the liquid than in the gas phase, probably due to smaller ionization potentials in the condensed phase (polarization energy effect). Field dependent electron mobilities are also reported.

Effect of Electric Field Strength on the Free Ion Yields in the X-Radiolysis of Liquids: Influence of Molecular Structure and Temperature

1972 ◽  
Vol 50 (11) ◽  
pp. 1617-1626 ◽  
Author(s):  
J.-P. Dodelet ◽  
P. G. Fuochi ◽  
G. R. Freeman
Keyword(s):  
Field Strength ◽  
Liquid Argon ◽  
Separation Distance ◽  
Relative Increase ◽  
Distribution Functions ◽  
Electron Pairs ◽  
Gaussian Distribution Function ◽  
Free Ion ◽  
Liquid Methane ◽  
Ion Yields

The relative increase in the free ion yield with increasing field strength E, expressed as [Formula: see text] is smaller when the following quantities are larger: (1) dielectric constant, (2) temperature, and (3) separation distance between the geminate ion–electron pairs. The field dependence [Formula: see text] equals 9.7/εT2 cm/V at low E, but at higher fields it is affected by the above three factors and by E itself. Results obtained from the liquids propane (123–233 °K), 2-methylpropane (isobutane, 148–294 °K), 2,2-dimethylpropane (neopentane, 295 °K), argon (87 °K), oxygen (87 °K) and argon–oxygen solutions (87 °K) are presented and analyzed according to a theoretical model. Several types of ion–electron separation (y) distribution functions are tested. Within the framework of the model a power function F(> y) = yminy−x with x < 4 provides a good interpretation of the results when [Formula: see text] a Gaussian distribution function provides the best interpretation of the field effects when [Formula: see text] Either the y distribution has a Gaussian core with a more gently sloping tail, or distributions are more Gaussian-like in liquids in which the electron ranges are greater. The electron range in pure argon (b = 1300 Å) is much smaller than had been expected and is only 2.6 times greater than that in liquid methane (b = 500 Å at 120 °K). Phonon emission by 10–0.01 eV electrons in liquid argon may be relatively efficient and might involve transient states of the type [Formula: see text]

Studies on the freezing of pure liquids I. Critical supercooling in molten alkali halides

1960 ◽  
Vol 259 (1298) ◽  
pp. 325-340 ◽  
Keyword(s):  
High Temperature ◽  
Critical Temperature ◽  
Melting Point ◽  
Alkali Halide ◽  
Alkali Halides ◽  
Solid Particles ◽  
High Supersaturation ◽  
Chamber Temperature ◽  
Reduced Temperature ◽  
Heater Coil

A high-temperature cloud chamber is described in which a bead of alkali halide is supported on a heater coil mounted in the roof. By passing the current through the coil the temperature of the bead may be momentarily raised by several hundred degrees, producing salt vapour at high supersaturation. Condensation ensues in the presence of the inert supporting gas, and clouds of droplets or solid particles appear depending on the chamber temperature. Light scattered from the clouds under strong illumination is examined with a telescope, and the presence of crystalline particles is detected by their capacity to scintillate, or ‘twinkle’. It is found that twinkling in clouds of alkali halides appears sharply as the temperature is lowered below the melting point, defining a critical temperature of solidification for each salt. Reasons are given for regarding this temperature as the freezing threshold of molten salt droplets, for which supercoolings of about 150 °C are indicated. A reduced temperature, given by the ratio of the freezing threshold to the melting point, has the value of approximately 0.8 for all the alkali halides examined.

scholarly journals MODELLING THE MELTING TEMPERATURE OF A LIPID‐BASED CRITICAL TEMPERATURE INDICATOR: A COMPARISION BETWEEN SIMPLEX-LATTICE AND SIMPLEX-CENTROID DESIGNS

2018 ◽  
Vol 35 (2) ◽  
Author(s):  
KARINE CRISTINE KAUFMANN ◽  
ODINEI HESS GONÇALVES ◽  
EVANDRO BONA ◽  
FERNANDA VITÓRIA LEIMANN
Keyword(s):  
Critical Temperature ◽  
Melting Point ◽  
Melting Temperature ◽  
Predictive Ability ◽  
Ternary Mixtures ◽  
Lipid Mixture ◽  
Color Changes ◽  
Lattice Design ◽  
Simplex Lattice ◽  
Improved Model

Critical temperature indicators (CTI) find applications in food industry in cases when defrost may not occur or a specific temperature may not be reached, , indicating changes through visual changes, such as melting, color changes, etc. Lipid mixtures are promising candidates to formulate CTI since the final melting point of the mixture may be manipulated by the proportion of each lipid. In this work a lipid mixture consisting of stearic acid, lard and peanut oil was used to develop a CTI mixture. Simplex-lattice and Simplex-centroid experimental designs were compared to modelling the melting temperature of the lipid mixture. Addition of axial points to the experimental design improved predictive ability of the models while the inclusion of inverse terms was necessary to improve models accuracy. Simplex-lattice design presented an improved ability to predict the melting point of binary mixtures, while the simplex-centroid design resulted in an improved model for predicting melting point of the ternary mixtures

scholarly journals The Ion Pair Thermal Model of MALDI MS

2021 ◽  
Author(s):  
Shiyue Fang
Keyword(s):  
Gas Phase ◽  
Thermal Model ◽  
Ion Pair ◽  
Pair Formation ◽  
Maldi Ms ◽  
Ion Extraction ◽  
Free Ion ◽  
Pair Separation ◽  
Ion Yields ◽  
Ion Pair Separation

The ion pair thermal model for MALDI MS is described. Key elements of the model include thermal desorption and ionization, strong tendency to neutralization via ion pair formation and proton transfer in the gas phase, thermal equilibrium, overall charge neutral plume, and thermal energy assisted free ion generation via ion pair separation by ion extraction potential. The quantities of ions in the solid sample and in the gaseous plume are estimated. Ion yields of different classes of molecules including peptides, nucleic acids, permanent salts and neutral molecules are estimated at the macroscale and single ion pair levels. The estimated ion yields are close to experimentally observed values under certain assumptions. Explanations of several observations in MALDI MS such as mostly single-charged peaks, improvement of spectra by ammonium cation, and ion suppression are provided. We expect that the model can give insights for the design of new conditions and systems for improving the sensitivity and resolution of MALDI MS and improving its capability and reliability to analyze large biomolecules.

Gas Supply and the Anaesthetic Machine

2011 ◽  
Author(s):  
Patrick Magee ◽  
Mark Tooley
Keyword(s):  
Critical Temperature ◽  
Anaesthetic Machine ◽  
Liquid Oxygen ◽  
Liquid Form ◽  
Relief Valve ◽  
Gaseous Oxygen ◽  
Hospital Building ◽  
Pass Through ◽  
Delivery Pipe ◽  
Gas Supply

In Europe and other advanced medical communities, medical gases are generally supplied by pipeline, with cylinders available as back up. Large hospitals usually have oxygen supplied and stored in liquid form, since one volume of it provides 840 volumes of gaseous oxygen at 15◦C. It is stored in a secure Vacuum Insulated Evaporator (VIE) on the hospital site. The arrangement is shown in Figure 22.1. The VIE consists of an insulated container, the inner layer of which is made of stainless steel, the outer of which is made of carbon steel. The liquid oxygen is stored in the inner container at about−160◦C (lower than the critical temperature of−118◦C) at a pressure of between 700 and 1200 kPa. There is a vapour withdrawal line at the top of the VIE, from which oxygen vapour can go via a restrictor to a superheater, where the gas is heated towards ambient temperature. Where demand exceeds supply from this route, there is also a liquid withdrawal line from the bottom of the VIE, from which liquid oxygen can be withdrawn; the liquid can be made to join the vapour line downstream of the restrictor and pass either through the superheater or back to the top of the VIE. The liquid can also be made to pass through an evaporator before joining the vapour line. After passing through the superheater, the oxygen vapour is passed through a series of pressure regulators to drop the pressure down to the distribution pipeline pressure of 410 kPa. It should be remembered that no insulation is perfect and there is a pressure relief valve on top of the VIE in case lack of demand and gradual temperature rise results in a pressure build up in the container. There is a filling port and there is usually considerable wastage in filling the VIE; the delivery hose needs to be cooled to below the critical temperature, using the tanker liquid oxygen itself to cool the delivery pipe. The whole VIE device is mounted on a hinged weighing scale and is situated outside the hospital building, protected by a caged enclosure, which also houses two banks of reserve cylinders.

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