Honglin Zhang

Resonant X-ray enhancement of the Auger effect in high-Z atoms, molecules, and nanoparticles: potential biomedical applications.

It is shown that X-ray absorption can be considerably enhanced at resonant energies corresponding to K-shell excitation into higher shells with electron vacancies following Auger emissions in high-Z elements and compounds employed in biomedical applications. We calculate Auger resonant probabilities and cross sections to obtain total mass attenuation coefficients with resonant cross sections and detailed resonance structures corresponding to Kalpha, Kbeta, Kgamma, Kdelta, and Keta complexes lying between 6.4-7.1 keV in iron and 67-80 keV in gold. The basic parameters were computed using the relativistic atomic structure codes and the R-matrix codes. It is found that the average enhancement at resonant energies is up to a factor of 1000 or more for associated K --> L, M, N, O, P transitions. The resonant energies in high-Z elements such as gold are sufficiently high to ensure significant penetration in body tissue, and hence the possibility of achieving X-radiation dose reduction commensurate with resonant enhancements for cancer theranostics using high-Z nanoparticles and molecular radiosensitizing agents embedded in malignant tumors. The in situ deposition of X-ray energy, followed by secondary photon and electron emission, will be localized at the tumor site. We also note the relevance of this work to the development of novel monochromatic or narrow-band X-ray emission sources for medical diagnostics and therapeutics.

Collision strengths and oscillator strengths for excitation to the n = 3 and 4 levels of neon-like ions

Collision strengths are given for the 88 possible fine-structure transitions between the ground level and the n = 3 and 4 levels in 20 neon-like ions with nuclear charge number Z in the range 18 less than or equal toZless than or equal to74. The results are given for the nine impact-electron energies in threshold units X = 1.0, 1.2, 1.5, 1.9, 2.5, 4.0, 6.0, 10.0, and 15.0. In addition, electric dipole oscillator strengths obtained by various methods are given. copyright 1987 Academic Press, Inc.

Collision strengths for innershell excitation of Li-like ions from the 1s22s and 1s22p levels to the 1s2l3l′ levels

Abstract Collision strengths, collision rates, transition energies, and electric-dipole radiative line strengths have been calculated for innershell excitation from the 1s22s and 1s22p levels to all levels of the 1s2l3l′ configurations in Li-like ions with nuclear charge number Z in the range 6 ⩽ Z ⩽ 74. The collision strengths, which are obtained using a Coulomb-Born-exchange method, are expressed in a convenient form in terms of the scaled hydrogenic ion collision strengths Z 2 Ω H and Z 2 Ω H e . Results for innershell excitation to the levels of the 1s2l2l′ configurations considered in earlier work are also expressed in this form. The calculations include configuration mixing, parentage mixing, and intermediate coupling effects.

Collision strengths and line strengths for all transitions among the levels of the 1s22s22p, 1s22s2p2, and 1s22p3 configurations of boron-like ions

Abstract Collision strengths and electric-dipole line strengths have been calculated for all fine-structure transitions among the levels of the 1 s 2 2 s 2 2 p , 1 s 2 2 s 2 p 2 , and 1 s 2 2 p 3 configurations in 17 boron-like ions with nuclear charge number Z in the range 10 ⩽ Z ⩽ 74. From these results the collision strengths and line strengths for transitions between energy terms and their analogs in jj coupling can also be obtained. The collision strength data cover impact-electron energies ⩽ 3.25 Z 2 Ry or 44.2 Z 2 eV. The effects of configuration mixing, parentage mixing, and intermediate coupling have been included in the calculations. The method used in calculating the collision strengths is a Coulomb-Born-Exchange method well suited for treating many members of an isoelectronic sequence simultaneously. The complete results have been given in terms of fits to simple functions of the impact-electron energy that are readily integrated over a Maxwellian distribution to obtain collision rates. Some discussion is given of important differences between the present method and the more usual Coulomb-Born-Exchange method, where it is assumed that the free electron sees the screened nuclear charge ( Z - N ).

Collision strengths and line strengths for all transitions among the levels of the 1s2l2l′ configurations of Li-like ions☆

Abstract Collision strengths and electric-dipole line strengths have been calculated for all fine-structure transitions among the levels of the 1 s 2 l 2 l ′ configurations in 19 Li-like ions with nuclear charge number Z in the range 6 ⩽ Z ⩽ 74. From these results the collision strengths and line strengths for transitions between energy terms and their analogs in jj coupling can also be obtained. The collision strength data cover impact-electron energies ⩽3.25 Z 2 Ry or 44.2 Z 2 eV. The effects of configuration mixing, parentage mixing, and intermediate coupling have been included in the calculations. The method used in calculating the collision strengths is a Coulomb-Born-Exchange method well suited for treating many members of an isoelectronic sequence simultaneously. The complete results have been given in terms of fits to simple functions of the impact-electron energy that are readily integrated over a Maxwellian distribution to obtain collision rates.