scholarly journals Zur Kinetik des monomolekularen Zerfalls organischer Ionen in hohen elektrischen Feldern

1966 ◽  
Vol 21 (11) ◽  
pp. 1920-1930
Author(s):  
H. D. Beckey ◽  
H. Knöppel
Keyword(s):  
Field Strength ◽  
Electric Fields ◽  
Mass Spectra ◽  
Resolving Power ◽  
Field Ionization ◽  
Time Interval ◽  
Dissociation Limit ◽  
Zero Field ◽  
Minute Amount ◽  
Molecular Ion

The kinetics of unimolecular decomposition of organic ions in the presence of electric fields up to 108 V/cm is discussed. The results are deduced from the mass spectra obtained by field ionization of organic molecules. The time interval between formation and decomposition of the ions can be derived from the shape of the mass lines. It is shown that field induced decomposition can occur at a minimum time of about 3 · 10–14 sec after field ionization. The optimum time resolution with these experiments, 10–12 sec, is given by the resolving power of the mass spectrometer.The results can be interpreted in terms of five different mechanisms :1. Field induced dissociation. Excitation of the molecular ion to a state above the dissociation limit is possible at high enough fields. Spontaneous dissociation within one vibrational period will then be possible because the excitation energy is contained in the reaction coordinate.2. Field induced dissociation by tunneling of radicals through the potential barrier. This may occur after excitation of the molecular ion to a state lying in an interval between the dissociation limit and about half a vibrational energy quantum below this, provided the field strength is high enough. The maximum observable life time of ions resulting from this process is about 6·10–12 sec.3. Field induced dissociation, delayed by re-orientation of the molecular ion. Certain orientations of the molecular ion are favoured with respect to field dissociation. The maximum re-orientation time for a favourable position is of the order 3·10–12 sec.4. Field induced statistical dissociation. This is due to fluctuation of energy within the ion, as in the case of common reaction kinetics, but with lowering of the dissociation limit by the field. The time intervall for these processes lies between about 10–13 and 10–11 sec.5. Statistical decomposition in the space of low or zero field strength. This process is due to energy fluctuation within the molecular ion excited to a state above the dissociation limit, lowered only by a minute amount by the weak field. The range of life times is about 10–11 to 10–8 sec. Processes of the same type, occurring at zero field strength within about 10–8 and 10–6 sec, are called — as usually — “metastable” processes.The processes described here are derived mainly from the FI mass spectra of paraffins, alcohols, ethers and ketones. Dissociation is hindered, in some cases, by high electric fields.

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.

A New Method for Surface Ionization of Organic Molecules by Attachment of Alkali Ions in Moderate Electric Fields

1975 ◽  
Vol 30 (12) ◽  
pp. 1685-1690 ◽  
Author(s):  
F. W. Röllgen ◽  
H.-R. Schulten
Keyword(s):  
Electric Fields ◽  
Mass Spectra ◽  
Organic Molecules ◽  
Field Ionization ◽  
Surface Ionization ◽  
Decomposition Products ◽  
Alkali Ions ◽  
Ionization Method ◽  
Simple Mass ◽  
Ion Attachment

Abstract It is shown that polar organic molecules may be ionized at metal surfaces by attachment of alkali ions in moderate electric fields. Lithium salts adsorbed on tungsten surfaces were employed for this method of ionization. The alkali ion attachment results from a surface reaction in the transition region between a thermal and field ionization. The particular advantage of this ionization method lies in the production of very simple mass spectra which contain no decomposition products of ions.

Electron-Mirror Microscopic Aspects of Ferroelectric Domains of BaTiO3 And Ca2Sr (C2H5CO2)6

1970 ◽  
Vol 28 ◽  
pp. 478-479
Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi
Keyword(s):  
Surface Layer ◽  
Electric Fields ◽  
Quantitative Study ◽  
Recent Progress ◽  
Ferroelectric Domain ◽  
Resolving Power ◽  
Surface Pattern ◽  
Crystal Surfaces ◽  
One Dimensional ◽  
Ferroelectric Domains

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).

On the Field Evaporation Behavior of a Model Ni-Al-Cr Superalloy Studied by Picosecond Pulsed-Laser Atom-Probe Tomography

2008 ◽  
Vol 14 (6) ◽  
pp. 571-580 ◽  
Author(s):  
Yang Zhou ◽  
Christopher Booth-Morrison ◽  
David N. Seidman
Keyword(s):  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Pulsed Laser ◽  
Picosecond Laser ◽  
Atom Probe ◽  
Resolving Power ◽  
Noise Levels ◽  
Thermally Activated ◽  
Mass Resolving Power

AbstractThe effects of varying the pulse energy of a picosecond laser used in the pulsed-laser atom-probe (PLAP) tomography of an as-quenched Ni-6.5 Al-9.5 Cr at.% alloy are assessed based on the quality of the mass spectra and the compositional accuracy of the technique. Compared to pulsed-voltage atom-probe tomography, PLAP tomography improves mass resolving power, decreases noise levels, and improves compositional accuracy. Experimental evidence suggests that Ni2+, Al2+, and Cr2+ ions are formed primarily by a thermally activated evaporation process, and not by post-ionization of the ions in the 1+ charge state. An analysis of the detected noise levels reveals that for properly chosen instrument parameters, there is no significant steady-state heating of the Ni-6.5 Al-9.5 Cr at.% tips during PLAP tomography.

Paraelektrische Resonanz und dielektrische Dispersion von Wasser in Beryll-Einkristallen / Paraelectric Resonance and Dielectric Dispersion of Water in Beryl Single Crystals

1974 ◽  
Vol 29 (11) ◽  
pp. 1558-1571
Author(s):  
H.-J. Rehm
Keyword(s):  
Electric Fields ◽  
Resonance Effect ◽  
Theoretical Description ◽  
Tunnel Effect ◽  
Zero Field ◽  
Zero Field Splitting ◽  
A Value ◽  
Axis Parallel ◽  
Electric Dipoles ◽  
The One

Paraelectric resonance spectra of beryl crystals are observed in the X-band region between 5 and 20 kV/cm under the condition that the external electric field F[101̅0]. Additional dielectric measurements show, that the paraelectric centres are the monomeric water molecules in the beryl cavities. For water dipoles in beryl only two orientations of the molecular a-axis relative to the crystal C6-axis are possible, and only those with their a-axis parallel to the C6-axis contribute to the paraelectric resonance effect. The electric moment vector µ of these latter molecules may rotate in the (0001)-crystal plane, i. e. around their own a-axis, and has a value of (1.9 ± 0.2) D. A theoretical description of paraelectric resonance is presented for a simplified model: the electric dipoles have 6 equivalent equilibrium positions along the [101̅0]-directions, tunnel effect and external electric fields remove the site degeneracy and we observe a molecular Stark splitting. We calculate a value of (2.0 ± 0.4) GHz for the zero-field splitting in the one-parameter Hamiltonian model.

scholarly journals Photoluminescence of CdSe/ZnS quantum dots in nematic liquid crystals in electric fields

2018 ◽  
Vol 9 ◽  
pp. 1544-1549 ◽  
Author(s):  
Margarita A Kurochkina ◽  
Elena A Konshina ◽  
Daria Khmelevskaia
Keyword(s):  
Quantum Dots ◽  
Liquid Crystals ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Dielectric Anisotropy ◽  
Vertical Position ◽  
Decay Times ◽  
Pl Intensity

We have experimentally investigated the effect of the reorientation of a nematic liquid crystal (LC) in an electric field on the photoluminescence (PL) of CdSe/ZnS semiconductor quantum dots (QDs). To the LC with positive dielectric anisotropy, 1 wt % QDs with a core diameter of 5 nm was added. We compared the change of PL intensity and decay times of QDs in LC cells with initially planar or vertically orientated molecules, i.e., in active or passive LC matrices. The PL intensity of the QDs increases four-fold in the active LC matrix and only 1.6-fold in the passive LC matrix without reorientation of the LC molecules. With increasing electric field strength, the quenching of QDs luminescence occurred in the active LC matrix, while the PL intensity did not change in the passive LC matrix. The change in the decay time with increasing electric field strength was similar to the behavior of the PL intensity. The observed buildup in the QDs luminescence can be associated with the transfer of energy from LC molecules to QDs. In a confocal microscope, we observed the increase of particle size and the redistribution of particles in the active LC matrix with the change of the electric field strength. At the same time, no significant changes occurred in the passive LC matrix. With the reorientation of LC molecules from the planar in vertical position in the LC active matrix, quenching of QD luminescence and an increase of the ion current took place simultaneously. The obtained results are interesting for controlling the PL intensity of semiconductor QDs in liquid crystals by the application of electric fields.

Zero-Field Level Crossing in the Helium Atom

1972 ◽  
Vol 50 (2) ◽  
pp. 116-118 ◽  
Author(s):  
C. W. T. Chien ◽  
R. E. Bardsley ◽  
F. W. Dalby
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Helium Atom ◽  
Cross Sections ◽  
Zero Field ◽  
Level Crossing ◽  
Field Level ◽  
Collision Cross Sections ◽  
The Magnetic Field

Zero-field level-crossing techniques have been used to measure some upper-state lifetimes of the helium atom. The half-widths of curves obtained by plotting the polarization against the magnetic field strength for the n1D–21D transitions yielded lifetimes of 2.03 × 10−8 s for the 31D state, 3.36 × 10−8 s for the 41D state, and 7.44 × 10−8 s for the 51D state. Collision cross sections for these 1D levels were also determined.

scholarly journals Electron Impact Ionization Mass Spectra of 3-Amino 6-Chloro2-methyl Quinazolin-4-(3H)-one Derivative

2021 ◽  
pp. 1-5
Author(s):  
Osarumwense Peter Osarodion ◽  
◽  
Omotade Treasure Ejodamen ◽  
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Impact Ionization ◽  
Cyclic Compound ◽  
Electron Impact Ionization ◽  
Ionization Mass ◽  
Fragmentation Pattern ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Characteristic Fragmentation

Looking at the previous studies on quinazolinones derivatives, only limited information’s are available on their mass spectral along with the preparation of novel quinazolin-4-(3H)-one derivatives The condensation of Methyl-2-amino-4-Chlorobenzoate with acetic anhydride yielded the cyclic compound 2-methyl 7-Chloro-1, 3-benzo-oxazine-4-one (1) which further produce 3-Amino-2-Methyl 7-Chloro quinazolin-4(3H)-ones (2) via the reaction with hydrazine hydrate. The compounds synthesized were unequivocally confirmed by means of Infrared, Nuclear Magnetic Resonance (1H and 13C), Gas Chromatography-Mass spectrophotometry and Elemental analysis. Discussion: The molecular ion of m/z 235 fragments to give m/z 220 by loss of –NH group. The ion of m/z 220 was broken to give m/z 206 by losing CH2 group and fragment to m/z 177 by loss of HCO. This fragmented to m/z 162 by loss of –CH3 group and then m/z 136 by loss of CN group. The loss of O gave m/z 120 which fragment to give m/z 93 by loss of –HCN and finally gave m/z 65 by loss of CO group. Conclusion: The electron impact ionization mass spectra of compound 2show a weak molecular ion peak and a base peak of m/z 235resulting from a cleavage fragmentation. Compound 2 give a characteristic fragmentation pattern. From the study of the mass spectra of compound 2, it was found that the molecular ion had fragmented to the m/z 220. The final fragmentation led to ion of m/z 93 and ion of mass m/z 65, respectively

scholarly journals SCIDOT-52. IN SITU DELIVERY OF TUMOR TREATING FIELDS THERAPY IN GLIOBLASTOMA PATIENTS

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi282-vi282
Author(s):  
Jeffrey Arle ◽  
Eric Wong ◽  
Anders Korshoej ◽  
Socrates Dokos ◽  
Ze’ev Bomzon ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Fields ◽  
Large Scale ◽  
Cell Damage ◽  
Human Head ◽  
Tumor Control ◽  
Electrode Arrays ◽  
Tumor Treating Fields ◽  
Newly Diagnosed Glioblastoma

Abstract The efficacy of Tumor-Treating Fields (TTFields) rests on the result of a large-scale clinical trial that demonstrated an increase in the survival of newly diagnosed glioblastoma patients when combined with temozolomide chemotherapy. Overall survival now extends to over 60 months in some of our patients when dexamethasone, which we suspected of interference with TTFields effects, is replaced with celecoxib to control tumor-associated inflammation. The transcranial method of delivering TTFields has not changed in light of ongoing advances in deep brain stimulation (DBS) and transcranial electric stimulation (TES), notably that the resistivity of the skull is the principle obstacle to placing therapeutic electric field strength of 2 V/cm into target tumor sites and variation in skull thickness is the main difference in TES efficiency across individuals. Realistic human head finite element modeling (FEM) predicted that surgical craniectomy beneath TTFields’ electrodes would enhance field strength at target tumor sites. Here we show that 2 V/cm can be reliably delivered to tumor sites using minimally-invasive DBS cylindrical leads or ribbon electrode arrays, pre- or post-resection. Two objections arise to the in situ method: 1) Will TTFields stimulate axons in situ? 2) Will field strength exceed safety limits for cell damage? Neural stimulation modeling and experiments show that TTFields’ frequency of 200 kHz, 1–3 orders of magnitude higher than ion channel time constants, is too high to stimulate them. Furthermore, 2 V/cm is well below cell damage limits of 700 V/mm. Thus we propose a new delivery method to improve tumor control in glioblastoma patients and to provide valuable information on TTFields’ effects via cell studies using in situ electric fields at 200 kHz.

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