Spherical Complex Optical Potential Research Articles

Electron impact total and ionization cross sections for Sr, Y, Ru, Pd, and Ag atoms

Calculation of electron impact total and ionization cross sections for Sr, Y, Ru, Pd, and Ag atoms were performed using spherical complex optical potential and complex scattering potential-ionization contribution methods. The complex optical potential model is formulated from the target parameters and the atomic charge density. The spherical charge densities are in turn derived from the Roothaan–Hartree–Fock wavefunctions defining the atomic orbital of the target. In the present study cross sections are computed in the energy range from ionization threshold to 2000 eV. The results obtained are compared with other theories and measurements wherever available and were found to be quite consistent and uniform. In general, present data show an overall reasonable agreement with other results. Dependence of total cross sections on the number of target electrons and peak of ionization cross section on target parameters were also found to be consistent with previous observations.

Electron impact total cross section calculations for CH3SH (methanethiol) from threshold to 5 keV

We report calculated total elastic cross sections Qel, total ionisation cross sections, Qion, summed total excitation cross sections ∑Qexc and total cross sections QT for CH3SH upon electron impact for energies from ionisation threshold to 5 keV. We have employed Spherical Complex Optical Potential (SCOP) formalism to calculate total elastic cross section Qel, and total inelastic cross section Qinel and used Complex Scattering Potential – the ionisation contribution (CSP-ic) method to extract the ionisation cross sections, Qion, from the calculated Qinel. The calculated total cross sections are examined as functions of incident electron energy and are compared with available data wherever possible and overall good agreement is observed. In this work Qel, Qion, and ∑Qexc are reported for the first time for CH3SH in this energy range.

Electron impact total ionization cross sections for all the components of DNA and RNA molecule

Present paper reports electron impact total ionization cross sections (Qion) for all the components of DNA and RNA molecules from threshold to 2000eV. We have employed spherical complex optical potential (SCOP) formalism to calculate the total inelastic cross sections and have deduced total ionization cross sections using complex scattering potential-ionization contribution (CSP-ic) method. DNA and RNA being the complex molecules, these cross sections are evaluated using the group additivity rule. The present results find good accord with the available previous theoretical estimates. In absence of experimental data for these biomolecules, the present theoretical estimates prove to be the reference data source. Qion for sugar phosphate backbone of RNA and for complete DNA and RNA units are reported for the first time in this work.

Electron impact total and ionization cross-sections for DNA based compounds

This paper reports computational results of the total (complete) and total ionization cross- sections, for electron impact on Uracil (C4H4N2O2) and PO3OH for impact energies from the ionization threshold to 2 keV. The total cross-section is evaluated using quantum mechanical approach using Spherical Complex Optical Potential (SCOP) presented as sum of the elastic and inelastic cross-sections. The ionization cross-sections are extracted from total inelastic cross-section using Complex Optical Potential–ionization contribution (CSP-ic) method. The present results are, in general, found to be in good agreement with previous theoretical results. In absence of any theoretical or experimental data, present results for PO3OH will serve to fill the void in the data base and may also inspire the experimentalists for some measurements as it is very important target.

Scattering of N2O on electron impact over an extensive energy range (0.1 eV–2000 eV)

We report electron impact total cross sections, Q(T), for e-N(2)O scattering over an extensive range of impact energies approximately from 0.1 eV to 2000 eV. We employ an ab initio calculation using R-matrix formalism below the ionization threshold of the target and above it we use the well established spherical complex optical potential to compute the cross sections. Total cross section is obtained as a sum of total elastic and total electronic excitation cross sections below the ionization threshold and above the ionization threshold as a sum of total elastic and total inelastic cross sections. Ample cross section data for e-N(2)O scattering are available at low impact energies and hence meaningful comparisons are made. Good agreement is observed with the available theoretical as well as experimental results over the entire energy range studied here.

Electron ionization of NF3

Experimental and theoretical study on electron ionization of NF3 is carried out in terms of the absolute partial and total ionization cross sections. The measurements are done in crossed electron beam-molecular beam geometry for electron incident energies ranging from 0 to 500eV using a newly built time of flight mass spectrometer with emphasis on complete collection, transmission and detection without mass and energy discrimination, while maintaining reasonable mass resolution. The cross sections are put on the absolute scale using the relative flow technique. The partial cross sections and the thresholds for the formation of NF3+, NF2+, NF+, F+, and N+ are compared with the previous results. Our cross section values for lower mass ions N+, F+, NF+ are found to be considerably higher as compared to previous measurements. We also have calculated the total scattering and total ionization cross sections using the spherical complex optical potential (SCOP) formalism and compared with existing data. While the total scattering calculations agree with the existing experimental results, the total ionization cross sections do not agree well with our experimental data. The present experimental results agree with those estimated using “Deutsch–Mark formulation with new additivity rules”, which were not in agreement with the existing experimental results for the case of NF3.

Computation of the total scattering cross sections for electron impact on HCl and HBr between 0.1 eV and 2000 eV

In this paper total cross sections (QT) for electron impact on HCl and HBr are reported over a wide energy range from circa 0.1 eV to 2 keV. At impact energies below the ionization energy, the R-Matrix method is employed using Quantemol-N software whilst above the ionization energy the spherical complex optical potential (SCOP) method is used. It is shown that the two methods provide complimentary cross sections where they overlap. These calculations are compared with experimental and theoretical results wherever available.

Calculations of total ionization cross sections for halogen compounds on electron impact from threshold to 2 keV

Calculation for electron impact total ionization cross sections on halogen compounds (BF, SiF, BCl, SiCl) are performed employing Spherical Complex Optical Potential and Complex Optical Potential — ionization contribution (CSP-ic) formalisms. In this article we are presenting data for energies ranging from above threshold to 2000 eV. Our results are compared with available experimental and theoretical data wherever available. It is found that the present result gives a better account of the ionization cross sections.

Electron impact total ionization cross sections for H 2S, PH 3, HCHO and HCOOH

This paper reports electron impact total ionization cross sections for molecules H 2S, PH 3, HCHO and HCOOH at energies circa threshold to 2 keV. Spherical Complex Optical Potential (SCOP) is the key ingredient in the Schrodinger equation to generate complex phase shifts and hence the total inelastic cross sections. Total inelastic cross section takes care of total loss of the flux into two dominant channels viz. total electronic excitation (discrete) and total ionization (continuum). We have employed Improved Complex Scattering Potential-ionization contribution (ICSP-ic) a semi empirical method to filter out ionization cross sections from total inelastic cross sections. The results are found to be in overall good agreement with most of the data available in the literature for all the presented targets.

Computation of the electron impact total ionization cross sections of C nH (2 n+1) OH molecules from the threshold to 2 keV energy range

Present paper reports calculations of total ionization cross sections ( Q ion) for simple but important alcohols (CH 3OH, C 2H 5OH, 1-C 3H 7OH) on electron impact with incident energies ( E i ) ranging from ionization threshold ( I) of the target to 2 keV. We have employed well established Spherical Complex Optical Potential (SCOP) formalism to evaluate total inelastic cross sections. We have also made an attempt to improve original Staszeweska model by considering Δ energy dependent and made to vary within the range ηI ≤ Δ( E i ) ≤ I. The total ionization cross sections are calculated using improved complex scattering potential-ionization contribution (ICSP-ic) method. The present results along with available experimental and other theoretical data are presented graphically.

Calculations of total and ionization cross-sections on electron impact for alkali metals (Li, Na, K) from threshold to 2 keV

In this article we report calculations of the total elastic, Q el , total ionization, Q ion , and total (complete), Q T , cross-sections for the targets Li, Na, K having low ionization thresholds and high polarizability upon electron impact for energies from circa threshold to 2000 eV. We have employed the well-known spherical complex optical potential (SCOP) formalism, which provides total elastic cross-section ( Q el ) and its inelastic counterpart ( Q inel ). The sum of Q el and Q inel gives the total (complete) cross-section, Q T , which is found to be very high at the lower energies (around 5 eV). This is attributed to high polarizabilities and low ionization thresholds of these atoms. Q inel includes Q ion and we have developed a semi-empirical method, called complex scattering potential-ionization contribution (CSP-ic) to extract ionization cross-sections from calculated total inelastic cross-section. Present calculations also provide information on the total excitation processes of these targets. The calculated cross-sections are examined as functions of incident electron energy along with available comparison and overall good agreement is observed.

Electron impact total ionization cross sections for halogens and their hydrides

Calculation for electron impact total ionization cross sections on halogen atoms (F, Cl, Br and I) and their hydrides (HF, HCl, HBr and HI) are performed employing Spherical Complex Optical Potential and Complex Optical Potential-ionization contribution formalisms. In this article we are presenting data for energies ranging from above threshold to 2000 eV. Our results are compared with available experimental and theoretical data wherever available. It is found that the present result gives a better account of the ionization cross sections.

Total cross sections of electron scattering by molecules NF3, PF3, N(CH3)3, P(CH3)3, NH(CH3)2, PH(CH3)2, NH2CH3 and PH2CH3 at 30–5000 eV

Total cross sections of electron scattering by eight molecules NF3, PF3, N(CH3)3, P(CH3)3, NH(CH3)2, PH(CH3)2, NH2CH3 and PH2CH3, which have some structural similarities, are calculated at the Hartree-Fork level by the modified additivity rule approach [D.H. Shi, J.F. Sun, Z.L. Zhu, H. Ma, Y.F. Liu, Eur. Phys. J. D 45, 253 (2007); D.H. Shi, J.F. Sun, Y.F. Liu, Z.L. Zhu, X.D. Yang, Chin. Opt. Lett. 4, 192 (2006)]. The modified additivity rule approach takes into considerations that the contributions of the geometric shielding effect vary as the energy of incident electrons, the dimension of target molecule, the number of electrons in the molecule and the number of atoms constituting the molecule. The present investigations cover the impact energy range from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories. Excellent agreement is observed even at energies of several tens of eV. It shows that the modified additivity rule approach is applicable to carry out the total cross section calculations of electron scattering by these molecules at intermediate and high energies, in particular over the energy range above 80 eV or so. It proves that the microscopic molecular properties, such as the geometrical size of the target and the number of atoms constituting the molecule, are of crucial importance in the TCS calculations. The new results for PH(CH3)2 and PH2CH3 are also presented at energies from 30 to 5000 eV, although no experimental and theoretical data are available for comparison. In the present calculations, the atoms are still represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.

Electron impact calculations of total ionization cross sections for environmentally sensitive diatomic and triatomic molecules from threshold to 5 keV

In this paper we report calculations of the total ionization cross sections, Qion, for environmentally sensitive molecules, namely CO, CO2, CS, OCS, CS2 and S2, upon electron impact for energies from circa threshold to 5000 eV. Spherical complex optical potential (SCOP) formalism is employed to evaluate total inelastic cross sections, Qinel. Total ionization cross sections, Qion, are extracted from the total inelastic cross sections, using a semi-empirical formalism developed by us, called the ‘complex spherical potential-ionization contribution’ (CSP-ic) method. The present results are compared with both theoretical and experimental data available in the literature and overall good agreement is observed for all the reported molecules.

Total cross sections of electron scattering by several sulfur-containing molecules OCS, SO2, SF4, SF6, SF5CF3, SO2Cl2 and SO2ClF at 30–5000 eV

Total cross sections of electron scattering by several sulfur-containing molecules OCS, SO2, SF4, SF6, SF5CF3, SO2Cl2 and SO2ClF are calculated at the Hartree-Fork level employing the modified additivity rule approach. The modified additivity rule approach, which was proposed by Shi et al. [Eur. Phys. J. D 45, 253 (2007); Nucl. Instrum. Meth. B 254, 205 (2007)], takes into consideration that the contributions of the geometric shielding effect vary as the energy of incident electrons, the target’s molecular dimension and the atomic and electronic numbers in the molecule. The present investigations cover the impact energies ranging from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories. Good agreement is observed even at energies of several tens of eV. It shows that the modified additivity rule approach is applicable to carry out the total cross section calculations of electron scattering by these sulfur-containing molecules at intermediate and high energies, especially over the energy range above 100 eV or so. In the present calculations, the atoms are still represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.

Screening-corrected electron impact total and ionization cross sections for boron trifluoride (BF3) and boron trichloride (BCl3)

In this paper, we report modified calculations for total elastic, total ionization and total (complete) cross sections for boron trifluoride (BF3) and boron trichloride (BCl3) upon electron impact at energies from around threshold to 2000 eV. We have proposed a model which allows screening correction due to the overlapping of atoms as seen by incident electrons in a complex molecule. We have employed the well-known spherical complex optical potential (SCOP) formalism to evaluate total elastic and total inelastic cross sections and hence total (complete) cross sections. The ionization cross sections were derived using the complex optical potential–ionization contribution (CSP-ic) method developed by us. The present results are compared with available experimental and other theoretical data wherever available and overall good agreement is observed. The present screening-corrected model shows improvement over the previous method especially at low energies. We also predict total elastic cross sections for these targets using this method.

Theoretical electron impact elastic, ionization and total cross sections for silicon hydrides, SiHx (x = 1, 2, 3, 4) and disilane, Si2H6 from threshold to 5 keV

In this article we report comprehensive calculations of total elastic (Qel), and total ionization cross sections, (Qion), on silicon hydrides SiHx (x = 1–4) and disilane, Si2H6 on electron impact at energies from circa threshold to 2000 eV and total (complete) cross sections (QT) up to 5 keV. Spherical complex optical potential (SCOP) formalism is employed to evaluate Qel and QT. Total ionization cross sections, Qion, are derived from total inelastic cross sections, Qinel, using our complex spherical potential – ionization contribution (CSP-ic) method. Dependence of QT on the dipole polarizability of the target and incident energy is presented for these targets through analytical formula, using which calculation of QT is extended up to 5 keV. Comparison of QT for all these targets is carried out to present a general theoretical picture of collision processes and also to visualize the dependence of QT on the total number of electrons in the target and hence on the geometrical size of the target. Present calculations also provide information on the excitation processes of these targets. Present results are compared with available experimental and other theoretical data wherever available and overall good agreement is observed. There is probably no data for total elastic and total (complete) cross sections for SiHx (x = 2-3) in the present energy range and hence reported for the first time.

Electron impact calculations of total and ionization cross-sections for Germanium Hydrides (GeH X; X = 1–4) and Digermane, Ge 2H 6

In this article we report calculations of the total elastic Q el, total ionization, Q ion, and total (complete), Q T, cross-sections for the germanium hydrides GeH X ( X = 1–4) and digermane (Ge 2H 6) upon electron impact for energies from circa threshold to 2000 eV. Spherical Complex Optical Potential (SCOP) formalism is employed to evaluate Q el, Q inel and Q T. Total ionization cross-sections, Q ion, are derived from the total inelastic cross-sections, Q inel, using a semi-empirical formulation developed by us called ‘Complex Spherical Potential-ionization contribution’ (CSP-ic) method. A comparison of the various cross-sections is provided to show their relative contribution to the total cross-section Q T. Present results are compared with available experimental and theoretical data wherever possible and overall agreement is good. However, no experimental data on the Q ion are available for the germanium hydrides, GeH X , X = 1–3 or digermane.

Geometric shielding correction approach for total cross sections of electron scattering by C6H6, C6F6, C6H12, C6H14, C6F14, C8H16, C8H18 and C8F18 at 30–5000 eV

Taking into consideration the contributions of the geometric shielding effect in the molecule, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. The total cross sections for electron scattering by eight larger polyatomic molecules (C6H6, C6F6, C6H12, C6H14, C8H16, C8H18, C6F14 and C8F18) are calculated using the new additivity rule at the Hartree–Fock level for impact energies ranging from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is attained above 100 eV or so. The new results for C6F14 and C8F18 are also presented although no experimental and theoretical data are available for comparison in the present energy region. In these calculations, the atoms are represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.

Calculations of elastic, ionization and total cross sections for inert gases upon electron impact: threshold to 2 keV

In this paper we report comprehensive calculations of total elastic (Qel), total ionization (Qion) and total (complete) cross sections (QT) for the impact of electrons on inert gases (He, Ne, Ar, Kr and Xe) at energies from about threshold to 2000 eV. We have employed the spherical complex optical potential (SCOP) formalism to evaluate Qel and QT and used the complex spherical potential-ionization contribution (CSP-ic) method to derive Qion. The dependence of QT on polarizability and incident energy is presented for these targets through an analytical formula. Mutual comparison of various cross sections is provided to show their relative contribution to the total cross sections QT. Comparison of QT for all these targets is carried out to present a general theoretical picture of collision processes. The present calculations also provide information, hitherto sparse, on the excitation processes of these atomic targets. These results are compared with available experimental and other theoretical data and overall good agreement is observed.