Electron impact ionisation cross sections of cis- and trans-diamminedichloridoplatinum(II) and its hydrolysis products

ABSTRACT

We report total electron-impact ionisation cross sections (EICSs) of cisplatin, its hydrolysis products and transplatin in the energy range from threshold to 10?keV using the binary-encounter-Bethe (BEB) and its relativistic variant (RBEB), and the Deutsch-Märk (DM) methods. We find reasonable agreement between all three methods, and we also note that the RBEB and the BEB methods yield very similar (almost identical) results in the considered energy range. For cisplatin, the resulting EICSs yield cross section maxima of 22.09?×?10^?20?m² at 55.4?eV for the DM method and 18.67?×?10^?20?m² at 79.2?eV for the (R)BEB method(s). The EICSs of monoaquated cisplatin yield maxima of 12.54?×?10^?20?m² at 82.8?eV for the DM method and of 9.74?×?10^?20?m² at 106?eV for the (R)BEB method(s), diaquated cisplatin yields maxima of 7.56?×?10^?20?m² at 118.5?eV for the DM method and of 5.77?×?10^?20?m² at 136?eV for the (R)BEB method(s). Molecular geometry does not affect the resulting EICS significantly, which is also reflected in very similar EICSs of the cis- and trans-isomer. Limitations of the work as well as desirable future directions in the research area are discussed.     

Autoionization cross section of potassium atom excited by electron impact

The autoionization cross section of potassium atoms excited by electron impact is measured in the energy range from the first autoionization threshold at 18.72 eV to 202 eV. The data are obtained by deter-mining the total intensity of electron spectra resulting from the decay of the 3p ⁵ n ₁ l ₁ n ₂ l ₂ autoionizing states. The cross section has two maxima, 1.8 × 10^?16 and 2.2 × 10^?16 cm², at 21 and 32 eV, respectively. The excitation dynamics of autoionization states suggests that the first maximum is associated with the resonance character of the near-threshold excitation. The second maximum, as well as the behavior of the cross section at energies above 50 eV, reflects the dynamics of electron excitation of quartet and doublet autoionizing states. The measured autoionization cross section is compared with known data for the total single ionization cross section of potassium atom by electron impact. The relative contribution of the autoionization cross section to the total single ionization cross section is found to reach 30% at 32 eV.     

Ionization function of magnesium for electron impact

Ionization cross sections for electron impact are measured with crossed beams of Mg atoms and pulsed electrons. Total numbers of particles are determined by the light emission of excited atoms. The ionization cross section obtained for electron energies from 7 eV to 60 eV has its maximum valueq _i (max)=7.8 · 10^?16 cm² at 12 eV electron energy.     

On the bound states in the muonic molecular ions

Absolute cross sections for electron impact ionization and dissociation of OH⁺ and OD⁺ leading to the formation of the OH²⁺, O⁺, O²⁺, O³⁺ and D⁺ ions have been measured by applying the animated electron-ion beam method in the energy range from the respective reaction thresholds up to 2.5 keV. The maximum of the single ionization cross section is found to be (0.95? ± ?0.02) × 10^?19 cm² at 155 eV. The maximum total cross sections for O⁺ and D⁺ fragments production are observed to be (15.7? ± ?0.2) × 10^?17 cm² at 95 eV and (10.8? ± ?0.5) × 10^?17 cm² at 95 eV, respectively. The cross sections for O²⁺ and O³⁺ are much smaller, (5.37? ± ?0.04) × 10^-18 cm² at 135 eV and (7.95? ± ? 0.23) × 10^-20 cm² at 315 eV, respectively. The collected data are analyzed in details in order to determine separately the contributions of dissociative excitation and of dissociative ionization to the O⁺ and D⁺ fragments production.     

Formation of positive and negative ions of thymine molecules under the action of slow electrons

The formation of positive and negative molecules of thymine—a base of nucleic acids—under the action of slow electrons is investigated by the method of crossed electron and molecular beams. The method developed makes it possible to measure the molecular beam intensity and determine the energy dependences and absolute values of total cross sections for the formation of positive and negative ions of thymine molecules. It is found that the maximal cross section for the formation of positive ions is reached at an energy of 95 eV and its absolute value is, accordingly, 1.4 × 10^?15 cm². The total cross section for the formation of negative ions is 8.2 × 10^–18 cm² at an energy of 1.1 eV. The mass spectra of thymine molecules are measured and the cross sections of dissociative ionization are determined.     

Electron-impact ionization and dissociation of C<Subscript>2</Subscript>D<Superscript>+</Superscript>

Absolute cross sections for electron-impact single ionization, dissociative excitation and dissociative ionization of the ethynyl radical ion (C₂D⁺)^+) have been measured for electron energies ranging from the corresponding reaction thresholds to 2.5 keV. The animated crossed electron-ion beam experiment is used and results have been obtained for the production of C₂D²⁺, C²⁺, C₂⁺_2^+ , CD⁺, C⁺ and D⁺. The maximum of the cross section for single ionization is found to be (2.01 ± 0.02) × 10^-17 cm², at the incident electron energy of 105 eV. Absolute total cross sections for the various singly charged fragments production are observed to decrease by a factor of almost three, from the largest cross-section measured for C⁺, over C₂⁺_2^+ and CD⁺ down to that of D⁺. The maxima of the cross sections are obtained to be (14.5 ± 0.5) × 10^-17 cm² for C₂⁺_2^+, (12.1 ± 0.1) × 10^-17 cm² for CD⁺, (27.7 ± 0.2) × 10^-17 cm² for C⁺ and (11.1 ± 0.8) × 10^-17 cm² for D⁺. The smallest cross section is measured to be (1.50 ± 0.04) × 10^-18 cm² for the production of the doubly charged ion C²⁺. Individual contributions for dissociative excitation and dissociative ionization are determined for each singly-charged product. The cross sections are presented in closed analytic forms convenient for implementation in plasma simulation codes. Kinetic energy release distributions of dissociation fragments are seen to extend from 0 to 6 eV for the heaviest fragment C₂⁺_2^+, up to 11.0 eV for CD⁺, 14.2 eV for C⁺ and 11.2 eV for D⁺ products.     

Cross section calculations for electron impact ionization and elastic scattering from cisplatin

Total cross section for single electron-impact ionization of cisplatin (H₆N₂Cl₂Pt) molecule has been calculated with the binary-encounter-Bethe (BEB) model from the ionization threshold up to 5 keV. To obtain input data for the BEB calculations, geometric and electronic structures of the cisplatin have been studied with quantum chemical methods. Elastic cross section for electron collisions with cisplatin have also been evaluated using independent atom method with static-polarization model potential for incident energies ranging from 50 to 3000 eV. The obtained geometric structure of cisplatin is compared with available experimental and theoretical data. Calculated cross sections have been compared with related cross sections for selected purine and pirimidine bases.     

Dissociative Excitation of Tetramethylsilane (TMS) and Hexamethyldisiloxane (HMDSO) by Controlled Electron Impact

The optical emission spectra in the wavelength region 200–800 nm produced by electron impact on the silicon-organic molecules TMS (tetramethylsilane) and HMDSO (hexamethyldisiloxane) under controlled single-collision conditions have been analyzed. Absolute emission cross sections from threshold to 200 eV impact energy were determined for a variety of emission features. For both targets, the CH(A²Δ → X²Π) emission, the so-called CH ?4300 Å”? band, was found to have the largest emission cross section with values (at 100 eV) of 5.5 × 10^?19 cm² and 6.1 × 10^?19 cm² for TMS and HMDSO, respectively. Relatively high onset energies of 28.0 ± 1.5 eV (TMS) and 33.1 ± 1.5 eV (HMDSO) were measured for these emissions. Weaker emission features in both spectra were identified as CH bands corresponding to the B²∑^? → X²Π transition (the CH ?3900 Å”? system) and the C²∑ → X²Π transition, and as the atomic Si line emissions at 253 nm and 288 nm. Near-threshold studies indicate an onset for the Si emissions of 29.0 ± 2.0 eV (TMS) and 44.6 ± 2.0 eV (HMDSO). Absolute cross sections and appearance energies were also determined for the strongest lines of the hydrogen Balmer series for both targets. The comparatively high onset energies and small emission cross sections for all observed emissions indicate that single-step dissociative excitation processes are unlikely to play a dominant role in low-temperature processing plasmas containing TMS and HMDSO.     

A radiotracer study of slow electron interaction with co on polycrystalline Mo

The interaction of slow (50–300 eV) electrons with CO chemisorbed on a polycrystalline Mo ribbon was investigated. A radiotracer was employed to monitor C concentration on the surface and desorbed ions were collected. From the time variation of the ion current, total electron induced desorption cross sections of 3.7 × 10^?17 to 1.6 × 10^?16 cm² were obtained. The desorption cross section for C containing species was found to be less than 1.4 × 10^?19 cm². In addition, the sticking coefficient for CO on Mo was found to be 0.13–0.16. These results are discussed in terms of the states of chemisorbed CO and the conclusions of other investigations of this systems.     

Double charge transfer in H+ + Mg Collisions

The total cross section for the reaction H⁺ + Mg → H^? + Mg⁺⁺ is calculated in the energy range of 10-10 000 eV. The double charge exchange cross section is large, rising to a maximum of 4× 10^?16 cm² at 100 eV.     

Electron-impact detachment from S<Superscript>-</Superscript>

Absolute cross sections for single and double electron-impact detachment of the S^- ion have been investigated over collision energy ranges of 0-60 eV and 0-30 eV, respectively. The experiment was performed at the ion storage ring, CRYRING. The threshold energies were measured to be 6.6 eV for single detachment and 19.8 eV in the case of double detachment. The single detachment cross section has a maximum of 6.7 x 10^-16 cm² at 30 eV. The double detachment cross section was studied only in the threshold region. No sharp structures were observed in either of the cross sections.Received: 24 April 2003, Published online: 29 July 2003PACS: 34.80.Dp Atomic excitation and ionization by electron impact - 34.80.Kw Electron-ion scattering; excitation and ionization     

Measurement of 4He(12C,16 O)γ Reaction in Inverse Kinematics

A cross section measurement employing a direct ¹⁶O detection method for the reaction energies from E _cm = 2.4 to 0.7 MeV is planned at Kyushu University Tandem Laboratory. To perform this experiment and to obtain quantitative information about the cross section to within an error of 10%, we have developed several instruments, including a blow-in type windowless gas target and a ionization chamber. A target thickness of 24 × 3.9 Torr cm was achieved using the developed gas target. The particle identification was successfully performed by using the energy deposit in the ionization chamber. Experiments were performed at E _cm = 2.4 and 1.5 MeV using the developed instruments and the cross sections were obtained.     

Characteristics of traps in TlInS2 single crystals

Characteristics of charge traps in TlInS₂ single crystals are investigated by the use of thermally stimulated current (TSC) technique. The TSC spectra of the sample from 80 K to 300 K are recorded at a constant heating rate. The spectra reveal that there are several trapping levels associated with the complex structure of overlapping peaks. The experimental results indicate that the traps in TlInS₂ associated with the spectra in the measuring range of temperature obey the monomolecular (first order) kinetics. Thus, the spectra are resolved into first order shaped peaks by the use of computerized best fit procedure. The trapping parameters; such as the energy depth, temperature dependent frequency factor and capture cross section, together with concentrations of the corresponding six discrete levels are computed. These centers all having low capture cross sections with strong temperature dependence are found to be at the energies of 0.11 eV, 0.22 eV, 0.25 eV, 0.26 eV, 0.29 eV and 0.30 eV with high concentrations of 6.6 × 10¹⁶, 2.0 × 10¹⁷, 3.3 × 10¹⁷, 9.6 × 10¹⁶, 2.3 × 10¹⁷ and 4.0 × 10¹⁷ cm^?3, respectively.     

Structure studies of neutron-rich beryllium and carbon isotopes

The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion induced transfer reactions. A strong sensitivity to the chosen core nucleus is found for the cores of ⁹Be and ¹⁰Be, respectively. With a ⁹Be core, molecular rotational bands up to high excitation energies are observed due to the pronounced 2α-cluster structure, whereas only few states at low excitation energies are populated with a ¹⁰Be core. For ¹¹Be a detailed investigation has been performed for the three states at 3.41 MeV, 3.89 MeV and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2⁺, 5/2^? and 3/2^?, respectively. Furthermore we have studied particlehole states of ¹⁶C using the ¹³C(¹²C,⁹C)¹⁶C reaction and found 14 previously unknown states.     

Rates and channels of water ionization by a high-current high-voltage pulsed discharge

The experimentally observed growth of the plasma density in a high-current high-voltage pulsed discharge in a liquid medium is compared with the results of calculations based on the effective cross sections for electron-impact ionization and other elementary processes. It is found that, in the initial stage of the discharge, the plasma density grows linearly with time, whereas at densities above 3 × 10¹⁰ cm^?3, the growth becomes exponential due to the collective acceleration of plasma electrons. The gas-vapor fraction of the water medium is ionized by two groups of electrons: low-energy electrons, with energies about several tens of electronvolts, and high-energy ones, with energies in the kiloelectronvolt range. The energy spent on water ionization is estimated and is found to be several times higher than the energy required to ionize a rarefied gas.     

Role of beryllium doping in strain changes in II-type InAs/GaSb superlattice investigated by high resolution X-ray diffraction method

We have studied the influence of the beryllium doping on strain in the II-type InAs/GaSb superlattices (SLs) by means of high-resolution X-ray diffraction (HRXRD). Three analyzed superlattices were grown by molecular beam epitaxy. One of the examined superlattices was undoped. Two others structures, called doped SLs, composed of two superlattices: Be-doped and undoped which were grown one on the top of each other. The doping concentration was determined by secondary ion mass spectroscopy. The doping level was 1×10¹⁷ cm^?3 and 2×10¹⁹ cm^?3. For doped superlattices, the HRXRD measurements showed splitting of satellite (ST) peaks. Furthermore, the separation of ST peaks increase with doping level. In contrast, for undoped superlattice, the splitting of the ST peaks was not observed. Sometimes the separation of ST peaks can be caused by change of thickness period of superlattice or partial relaxation of the structure. However, we claim that in our experiment the splitting is caused by another mechanism: The presence of Be atoms in SL causes the change of average lattice constant of the superlattice. The influence of Be dopant on lattice parameter of superlattice was confirmed by theoretical simulations. Furthermore, the change of the lattice constant (Δa/a) of the GaSb:Be buffer was examined. The reduction of lattice parameter of GaSb was noticed. It was caused by the presence of Be doping and unintentionally incorporated As-atoms in the GaSb layer. It is very important to know that even very small Be concentration (1×10¹⁷ cm^?3) causes the change of average lattice parameter of SL.     

Elastic scattering of the conduction electrons by adsorbed hydrogen

The cross section of adsorbed hydrogen for the conduction electrons is evaluated according to the Boltzmann-Fuchs equation, the Greene and Soffer theories for surface scattering of the conduction electrons and to the change of the electrical resistivity due to hydrogen adsorbed on evaporated nickel films obtained experimentally by Suhrmann et al. The calculated cross sections are 2.0 × 10^?15 cm² and 1.8 × 10^?15 cm² at 273°K and 90°K respectively at a low coverage of hydrogen, which are consistent with the theoretical value 3.0 × 10^?15 cm² by Toya and reasonable compared with 0.9 × 10^?15 cm², the cross section of a gaseous hydrogen atom. The cross section decreases with increase of the coverage. This change is considered to be closely related to that of the heat of adsorption.     

Single-electron charge transfer and excitations at collisions between Bi<Superscript>4+</Superscript> ions in the kiloelectronvolt energy range

Pioneering theoretical data for single-electron charge transfer and excitations due to collisions between Bi⁴⁺ ions in the ground (6s) and metastable (6p) states are gained in the collision energy interval 5–75 keV in the center-of-mass frame. The cross sections of the processes are calculated in terms of the close-coupling method in the basis of two-electron quasi-molecular states for the Coulomb trajectory of nuclei. It is found that single-electron capture into the singlet 6s ² states of Bi³⁺ ions makes a major contribution to the charge transfer total cross section for Bi⁴⁺(6s) + Bi⁴⁺(6s) collisions (reaction 1), whereas single-electron capture into the singlet 6s6p states is the basic contributor to the total cross section in Bi⁴⁺(6s) + Bi⁴⁺(6p) collisions (reaction 2). In the collision energy interval mentioned above, the collision cross sections vary between 1.2 × 10^?17 and 1.9 × 10^?17 cm² for reaction 1 and between 3.8 × 10^?17 and 5.3 × 10^?17 cm² for reaction 2. In reaction 1, the 6s → 6p excitation cross sections vary from 0.6 × 10^?16 to 0.8 × 10^?16 cm² for the singlet channel and from 2.2 × 10^?16 to 2.8 × 10^?16 cm² for the triplet channel. The calculation results are compared with the data obtained in experiments with crossed ion beams of kiloelectronvolt energy. The fraction of metastable ions in the beams is estimated by comparing the experimental data with the weighted average theoretical results for the cross sections of reactions 1 and 2. From the data for the charge transfer cross sections, one can estimate particle losses in relativistic beams due to a change in the charge state of the ions colliding with each other in the beam because of betatron oscillations.     

Cross sections for slow ion production and charge transfer in H+3(D+3)−H2(D2) collisions

Slow ion production cross sections for collisions of H⁺₃ and D⁺₃ ions with H₂ and D₂ have been measured at collision energies between 100 eV and 500 eV. The values vary from 2 × 10^-17 cm² to 6 × 10^-17 cm². The smaller cross sections for D₃ projectiles may be explained as an internal energy effect.