Electron correlation in fast ion-impact single ionization of helium atoms

A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections（FDCS） for proton-impact single ionization of helium atoms in their ground states. The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically. Calculations are performed in the scattering and perpendicular planes. The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets. An illustrative computation is performed for 75-ke V proton–helium collisions and the obtained results are compared with experimental data and other theoretical predictions. Although for small momentum transfers, the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes, some significant discrepancies are still present at large momentum transfers in these planes. However, our results are compatible and for some cases, better than those of the other sophisticated calculations.

Scaling law of single ion–atom impact ionization cross sections of noble gases from He to Xe at strong perturbative energies

We extend our previous work of a classical over-barrier ionization （COBI） model to calculate the single ionization cross sections of noble gases ranging from He to Xe at strong perturbative energies. The calculation results are in good agreement with extensive experimental data. The scaling law of single ion-atom impact ionization cross sections of noble gases on projectile charge q and energy E, also on target ionization energy I is drawn from the model.

Chirp-dependent ionization of hydrogen atoms in the presence of super-intense laser pulses

We perform a theoretical study on dynamic interference in single photon ionization of ground state hydrogen atoms in the presence of a super-intense ultra-fast chirped laser pulse of different chirp types(equal-power and equal-FWHM laser pulses)by numerically solving the time-dependent Schrödinger equation in one dimension.We investigate the influences of peak intensity and chirp parameters on the instantaneous ionization rate and photoelectron yield,respectively.We also compare the photoelectron energy spectra for the ionization by the laser pulses with different chirp types.We find that the difference between the instantaneous ionization rates for the ionization of hydrogen atom driven by two different chirped laser pulses is originated from the difference in variation of vector potentials with time.

Ionizing radiation effect on single event upset sensitivity of ferroelectric random access memory

The impact of ionizing radiation effect on single event upset（SEU） sensitivity of ferroelectric random access memory（FRAM） is studied in this work. The test specimens were firstly subjected to ^60Co γ-ray and then the SEU evaluation was conducted using ^209Bi ions. As a result of TID-induced fatigue-like and imprint-like phenomena of the ferroelectric material, the SEU cross sections of the post-irradiated devices shift substantially. Different trends of SEU cross section with elevated dose were also found, depending on whether the same or complementary test pattern was employed during the TID exposure and the SEU measurement.

Triple differential cross sections of magnesium in doubly symmetric geometry

A dynamically screened three-Coulomb-wave （DS3C） method is applied to study the single ionization of magnesium by electron impact. Triple differential cross sections （TDCS） are calculated in doubly symmetric geometry at incident energies of 13.65, 17.65, 22.65, 27.65, 37.65, 47.65, 57.65, and 67.65 eV. Comparisons are made with experimental data and theoretical predictions from a three-Coulomb-wave function （3C） approach and distorted-wave Born approximation （DWBA）. The overall agreement between the predictions of the DS3C model and the DWBA approach with the experimen- tal data is satisfactory.

Protonated acetone ion chemical ionization time-of-flight mass spectrometry for real-time measurement of atmospheric ammonia

Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultraviolet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.%high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A signal normalization processing method was designed,and with this new method,the quantitative relative standard deviation(RSD)of the instrument was decreased from 17.5%to9.1%,and the coefficient of determination was increased from 0.8340 to 0.9856.The humidity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signalto-noise ratio S/N=3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.

Radiofrequency field enhanced chemical ionization with vacuum ultraviolet lamp for miniature time-of-flight mass spectrometer

It is difficult to rapidly and on-line detect trace volatile organic compounds for miniature massspectrometry due to its limited sampling volume at slow pumping speed. In this paper, we developed anew radiofrequency field enhanced chemical ionization source （RF-ECI） with vacuum ultraviolet （VUV）lamp by coupling radiofrequency electric field and direct-current field together. The experiment resultsshowed that the sensitivity of benzene, toluene, hydrogen sulfide and other compounds increased by 2-3orders of magnitude under the introduction of RF-ECI comparing to traditional single photon ionization（SPI）. At the same time, the reagent ion of O2＋ realized the charge transfer reaction chemical ionization,and the RF-ECI effectively expanded the detection range of the VUV lamp based SPI. The VUV lamp hasinherent advantages in the on-site analytical instrument for its small size and low power consumption,and the VUV lamp based RF-ECI miniature time-of-flight mass spectrometer （TOFMS） has a limit-of-detection for H2S as low as 0.0571 mg/m3, and it is expected to be used widely in the field of on-site rapidanalvsis.