Electron Mobilities and Ranges in Liquid Hydrocarbons: Cyclic and Polycyclic, Saturated and Unsaturated Compounds

1975 ◽  
Vol 53 (18) ◽  
pp. 2714-2728 ◽  
Author(s):  
Kyoji Shinsaka ◽  
Jean-Pol Dodelet ◽  
Gordon R. Freeman
Keyword(s):  
Energy Transfer ◽  
Inverse Function ◽  
Negative Ion ◽  
Methyl Groups ◽  
Molecular Symmetry ◽  
Solvated Electrons ◽  
Thermal Electron ◽  
Secondary Electrons ◽  
Cyclic Olefins ◽  
Ion Yields

Penetration ranges bGp of secondary electrons into 21 X-irradiated liquids were estimated from measured free ion yields. The density normalized ranges bGpd are independent of temperature. Increasing the molecular symmetry by creating one or more cycles in the molecule causes the normalized range to increase, provided that the amount of bond distortion due to strain remains small. Ranges are smaller in compounds that contain strained rings. Energy transfer from the secondary electrons to the molecules is enhanced by the presence of distorted bonds in the molecules. The ranges in olefins are affected by the same factors as those in saturated hydrocarbons, with the addition of a contribution of transient negative ion states to the energy transfer processes. Shielding the double bond by methyl groups is not effective; the effect of the added methyl groups on the molecular symmetry is a more important factor. The magnitude of the energy transfer interaction is an inverse function of molecular symmetry.The general correlation between bGp and thermal electron mobilities ue in liquids contains significant variations within it. For a given value of bGp, ue in different liquids increases in the order n-alkane < cycloalkane < cycloalkene < 1,4-cyclohexadiene or benzene. Arrhenius plots of ue in cyclic olefins curve downwards at low temperatures, due to the formation of a deeper trapped state of the electron. The trap is deepest in 1,4-cyclohexadiene (21 kcal/mol) and is attributed to an equilibrium between solvated electrons and anions at temperatures below about 280 K.

Epithermal Electron Ranges and Thermal Electron Mobilities in Liquid Aromatic Hydrocarbons

1974 ◽  
Vol 52 (20) ◽  
pp. 3495-3506 ◽  
Author(s):  
Kyoji Shinsaka ◽  
Gordon R. Freeman
Keyword(s):  
Aromatic Hydrocarbons ◽  
Secondary Electron ◽  
Shielding Effect ◽  
Methyl Groups ◽  
Thermal Electron ◽  
Molecular Asymmetry ◽  
Trimethyl Benzene ◽  
Free Ion ◽  
Benzene Toluene ◽  
Ion Yields

Radiolysis free ion yields were measured as functions of electric field strength and temperature in benzene, toluene, 1,2-, 1,3-, and 1,4-dimethylbenzene, 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzene, 1,2,3,4- and 1,2,4,5-tetramethylbenzene, pentamethylbenzene, hexamethylbenzene, naphthalene, and anthracene. Secondary electron ranges bGP were estimated from the yields. The density-normalized ranges bGPd were almost constant, 34−38 × 10−8 g/cm2, from benzene up to the tetramethylbenzenes, then increased to 47 × 10−8 in pentamethyl- and 52 × 10−8 in hexamethylbenzene. In naphthalene and anthracene the normalized ranges were 32 and ∼20 × 10−8 g/cm2, respectively. Electron mobilities in the liquids at 293 K, and their activation energies, expressed in (cm2/V s, kcal/mol) were: benzene (0.114, 7.4); toluene (0.063, 3.4); 1,2-dimethylbenzene (0.018, 4.4); 1,3-dimethylbenzene (0.057, 4.5); 1,4-dimethylbenzene (0.062, —); 1,2,3-trimethylbenzene (0.022, 4.8); 1,2,4-trimethylbenzene (0.035, 4.3); 1,3,5-trimethyl-benzene (0.17, 3.2); 1,2,3,4-tetramethylbenzene (∼0.02, 5). The mobilities reflect migration retarding influences of the aromatic ring and molecular asymmetry, and a slight ring-shielding effect of methyl groups that tends to enhance the mobility.

Mobilities and Ranges of Electrons in Liquids: Effect of Molecular Structure in C5–C12 Alkanes

1972 ◽  
Vol 50 (16) ◽  
pp. 2667-2679 ◽  
Author(s):  
Jean-Pol Dodelet ◽  
Gordon R. Freeman
Keyword(s):  
Inelastic Scattering ◽  
Cross Sections ◽  
Electron Mobility ◽  
Electron Interaction ◽  
Thermal Electron ◽  
Secondary Electrons ◽  
In Series ◽  
The Difference ◽  
Branched Chain ◽  
Ion Yields

X-radiolysis free ion yields and electron mobilities were measured in a series of branched chain hydrocarbons at several temperatures. The numbers listed after the following compounds are the temperature (K), Gfi, most probable penetration range of the secondary electrons (Å) and thermal electron mobility (cm2/V s): 2,2-dimethylpropane (neopentane), 294, 1.09, 213, 50; 2,2,3,3-tetramethylbutane, 379, 0.80, 130, –; 2,2,4,4-tetramethylpentane, 295, 0.83, 158, 24; 2,2,5,5-tetramethylhexane, 293, 0.67, 138, 12; 2,2,6,6-tetramethylheptane, 293, 0.47, 113, –; 2,2,7,7-tetramethyloctane, 383, 0.58, 100, –; 2,2,3,3-tetramethylpentane, 295, 0.42, 102, 5.2; cyclohexane, 294, 0.16, 67, 0.45. The difference between the activation energies of the reactions[Formula: see text]and[Formula: see text]is (E15–E14) ≈ (2 to 3)RT for twenty two different hydrocarbons, including olefins and benzene. The rate of energy loss by epithermal electrons in liquid hydrocarbons increases with increasing anisotropy of polarizability of the molecules or groups; the range of the electron interaction in a given molecule appears to be about two C—C bonds in series (groups up to neopentyl in size). There is a correlation between the mobilities of thermal electrons in liquids and the penetration ranges of the secondary electrons in the liquids. The electron mobility in a liquid alkane appears to be limited by inelastic scattering. The inelastic scattering cross sections for both thermal (< 0.1 eV) and epithermal (~ 1 eV) electrons in liquid alkanes are affected in similar ways by the anisotropy of polarizability of the molecules. In both instances the scattering apparently involves rotational (librational) excitation of the medium.

Effect of hydrocarbon solutes on electron ranges and free ion yields in liquid xenon

1978 ◽  
Vol 56 (6) ◽  
pp. 749-755 ◽  
Author(s):  
Toyoaki Kimura ◽  
Gordon R. Freeman
Keyword(s):  
Energy Transfer ◽  
Energy Transfer Process ◽  
Energy Transfer Efficiency ◽  
Negative Ion ◽  
Liquid Xenon ◽  
Efficiency Ratio ◽  
Free Ion ◽  
Trans Butene ◽  
Central Bond ◽  
Ion Yields

The energy transfer efficiency ratio, ETE=(σhΔEh/σxΔEx), for hydrocarbons dissolved in liquid xenon has the following values: ethane, 96; propane, 180; n-butane, 485; ethylene, 193; propylene, 255; cis-butene-2, 425; trans-butene-2, 665. The large increase on going from propane to butane is attributed to the energy absorption capability of the C2H5 groups through rotation about the central bond in butane. The presence of a double bond in the molecule enhances ETE, presumably through the participation of transient negative ion states in the energy transfer process. The cis–trans effect in butene-2 is still not understood.

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.

scholarly journals The quest for AMS of 182Hf – why poor gas gives pure beams

2020 ◽  
Vol 232 ◽  
pp. 02003
Author(s):  
Martin Martschini ◽  
Johannes Lachner ◽  
Silke Merchel ◽  
Alfred Priller ◽  
Peter Steier ◽  
...  
Keyword(s):  
Detection Efficiency ◽  
Ion Source ◽  
Negative Ion ◽  
Complete Suppression ◽  
Buffer Gas ◽  
Novel Approach ◽  
First Results ◽  
Ion Laser ◽  
R Process ◽  
Ion Yields

The long-lived radioisotope 182Hf (T1/2 = 8.9 Ma) is of high astrophysical interest as its potential abundance in environmental archives would provide insight into recent r-process nucleosynthesis in the vicinity of our solar system. Despite substantial efforts, it could not be measured at natural abundances with conventional AMS so far due to strong isobaric interference from stable 182W. Equally important is an increase in ion source efficiency for the anions of interest. The new Ion Laser InterAction Mass Spectrometry (ILIAMS) technique at VERA tackles the problem of elemental selectivity in AMS with a novel approach. It achieves near-complete suppression of isobar contaminants via selective laser photodetachment of decelerated anion beams in a gas-filled radio-frequency quadrupole (RFQ) ion cooler. The technique exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Alternatively, these differences in EA can also facilitate anion separation via chemical reactions with the buffer gas. We present first results with this approach on AMS-detection of 182Hf. With He +O2 mixtures as buffer gas in the RFQ, suppression of 182WF5− vs 180HfF 5− by >105 has been demonstrated. Mass analysis of the ejected anion beam identified the formation of oxyfluorides as an important reaction channel. The overall Hf-detection efficiency at VERA presently is 1.4% and the W-corrected blank value is 182Hf/180Hf = (3.4 ± 2.1)×10−14. In addition, a survey of different sample materials for highest negative ion yields of HfF 5− with Cs-sputtering has been conducted.

A pulse radiolysis study of solvated electrons in tert-butanol/water solutions

1986 ◽  
Vol 64 (8) ◽  
pp. 1548-1552
Author(s):  
Joanna Cygler ◽  
Norman V. Klassen ◽  
Carl K. Ross
Keyword(s):  
Experimental Data ◽  
Pulse Radiolysis ◽  
Oh Radicals ◽  
Solvated Electrons ◽  
Secondary Electrons ◽  
Water Solutions ◽  
Tert Butanol

Many solutes, added to water in amounts of a few mol%, cause an increase in the yield of solvated electrons (es−) measured by pulse radiolysis. A pulse radiolysis study of tert-butanol (tBuOH) in D2O has been carried out to investigate this phenomenon. Detailed measurements of the yield, measured as Gεmax(es−), and the deeay of solvated electrons were made at 6, 25, and 46 °C over the range 0–5mol% tBuOH. The maximum Gεmax(es−) occurs at about 1 mol% tBuOH, but the exact concentration depends on the temperature of the sample and the time after the pulse at which the measurement is made. Three factors are examined as contributing to the increased Gεmax(es−) in the presence of tBuOH and certain other solutes. They are (i) the change in viscosity produced by the added solute, (ii) the scavenging of OH radicals by the solute, thereby reducing the reaction of OH with es− and (iii) the possibility that the addition of the solute leads to an increase in the thermalization distance of the secondary electrons. It is concluded that effects (i) and (ii) are sufficient to explain the existing experimental data.

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