Plasma probe characteristics in low density hydrogen pulsed plasmas

Probe theories are only applicable in the regime where the probe's perturbation of the plasma can be neglected. However, it is not always possible to know, a priori, that a particular probe theory can be successfully applied, especially in low density plasmas. This is especially difficult in the case of transient, low density plasmas. Here, we applied probe diagnostics in combination with a 2D particle-in-cell model, to an experiment with a pulsed low density hydrogen plasma. The calculations took into account the full chamber geometry, including the plasma probe as an electrode in the chamber. It was found that the simulations reproduce the time evolution of the probe IV characteristics with good accuracy. The disagreement between the simulated and probe measured plasma density is attributed to the limited applicability of probe theory to measurements of low density pulsed plasmas. Indeed, in the case studied here, probe measurements would lead to a large overestimate of the plasma density. In contrast, the simulations of the plasma evolution and the probe characteristics do not suffer from such strict applicability limits. These studies show that probe theory cannot be justified through probe measurements

Numerical and experimental studies of the carbon etching in EUV-induced plasma

We have used a combination of numerical modeling and experiments to study carbon etching in the presence of a hydrogen plasma. We model the evolution of a low density EUV-induced plasma during and after the EUV pulse to obtain the energy resolved ion fluxes from the plasma to the surface. By relating the computed ion fluxes to the experimentally observed etching rate at various pressures and ion energies, we show that at low pressure and energy, carbon etching is due to chemical sputtering, while at high pressure and energy a reactive ion etching process is likely to dominate

Time-resolved and continuous-wave optical spin pumping of semiconductor quantum wells

Experimental and theoretical studies of all-optical spin pump and probe of resident electrons in CdTe/(Cd,Mg)Te semiconductor quantum wells are reported. A two-color Hanle-MOKE technique (based on continuous-wave excitation) and time-resolved Kerr rotation in the regime of resonant spin amplification (based on pulsed excitation) provide a complementary measure of electron spin relaxation time. Influence of electron localization on long-lived spin coherence is examined by means of spectral and temperature dependencies. Various scenarios of spin polarization generation (via the trion and exciton states) are analyzed and difference between continuous-wave and pulsed excitations is considered. Effects related to inhomogeneous distribution of $g$-factor and anisotropic spin relaxation time on measured quantities are discussed.Comment: 26 pages, 19 figures, submitted to special issue on Optical Orientation of Semiconductor Science and Technolog

Suppression of electron spin relaxation in Mn-doped GaAs

We report a surprisingly long spin relaxation time of electrons in Mn-doped p-GaAs. The spin relaxation time scales with the optical pumping and increases from 12 ns in the dark to 160 ns upon saturation. This behavior is associated with the difference in spin relaxation rates of electrons precessing in the fluctuating fields of ionized or neutral Mn acceptors, respectively. For the latter the antiferromagnetic exchange interaction between a Mn ion and a bound hole results in a partial compensation of these fluctuating fields, leading to the enhanced spin memory.Comment: 4 pages, 4 figure

Simulation of Time-Resolved Vibronic Spectra and the possibility of analyzing molecules with similar apectral properties

The possibility of using time-resolved vibronic spectroscopy for spectral analysis of mixtures of chemical compounds with similar optical properties, when traditional methods are inefficient, is demonstrated by using the method of computer simulation. The analysis is carried out by the example of molecules of a series of polyenes (butadiene, hexatraene, octatetraene, decapentaene, and decatetraene), their various cis- and trans-rotational isomers, and phenyl-substituted polyenes. Ranges of relative concentrations of molecules similar in their spectral properties, where reliable interpretation of time-resolved spectra of mixtures and both qualitative and quantitative analyses are possible, are determined. The use of computer simulation methods for oprimizing full-scale experiments in femtosecond spectroscopy is shown to hold much promise

Influence of the type of anaesthetic support on the development of postoperative cognitive dysfunction in gynecologic oncology patients

Aim. Determination of the influence of age and type of anesthesia on the patient’s cognitive abilities. Methods. 30 females who underwent surgical intervention were examined. The first group consisted of 14 patients who received general inhalational anesthesia, group 2 included 16 patients who received general inhalational anesthesia in combination with epidural anesthesia. All patients underwent neuropsychological testing at several stages: one day before the surgery, the first day after surgery, on day 28 after the surgery. Cognitive status was assessed using Mini-Mental State Examination (MMSE) and the clock-drawing test (CLOCK). Results. Given the combination of indices of both types of neuropsychological testing, postoperative cognitive dysfunction was diagnosed when a decrease by 10% or more of both MMSE and clock-drawing test and the MMSE score in patients with diagnosed postoperative cognitive dysfunction was less than 24 on both days 1 and 28. It should be noted that the results of testing before surgery in all groups of patients showed mild cognitive dysfunction. After the surgery, the measures of intellectual ability significantly decreased. The results of the analysis in the early recovery period in the group of patients who underwent combined anesthesia were significantly higher. And in the group of patients with combined anesthesia compared to the group that received only general anesthesia on day 28, cognitive indices were significantly higher: MMSE — pMW=0.041 and CLOCK — pMW Conclusion. General anesthesia combined with epidural anesthesia affects cognitive function of female patients less negatively than the use of general anesthesia alone

Stability of trions in strongly spin-polarized two-dimensional electron gases

Low-temperature magneto-photoluminescence studies of negatively charged excitons (X- trions) are reported for n-type modulation-doped ZnSe/Zn(Cd,Mn)Se quantum wells over a wide range of Fermi energy and spin-splitting. The magnetic composition is chosen such that these magnetic two-dimensional electron gases (2DEGs) are highly spin-polarized even at low magnetic fields, throughout the entire range of electron densities studied (5e10 to 6.5e11 cm^-2). This spin polarization has a pronounced effect on the formation and energy of X-, with the striking result that the trion ionization energy (the energy separating X- from the neutral exciton) follows the temperature- and magnetic field-tunable Fermi energy. The large Zeeman energy destabilizes X- at the nu=1 quantum limit, beyond which a new PL peak appears and persists to 60 Tesla, suggesting the formation of spin-triplet charged excitons.Comment: 5 pages (RevTex), 4 embedded EPS figs. Submitted to PRB-R