scholarly journals Time-resolved studies of low-temperature, EUV-induced plasmas: EUV emission in selected spectral ranges

2019 ◽  
Vol 37 (4) ◽  
pp. 400-407 ◽  
Author(s):  
A. Bartnik ◽  
H. Fiedorowicz ◽  
P. Wachulak ◽  
T. Fok
Keyword(s):  
Low Temperature ◽  
Excited States ◽  
Extreme Ultraviolet ◽  
Detection System ◽  
Time Duration ◽  
Time Resolved ◽  
Euv Emission ◽  
Decay Times ◽  
Driving Pulse ◽  
Spectral Ranges

AbstractInteraction of extreme ultraviolet (EUV) pulses of high intensity with gases results in the creation of non-thermalized plasmas. Energies of the driving photons and photoelectrons are sufficient for creation of excited states, followed by emission of the EUV photons. In most cases, decay times of these states are short comparing to the driving EUV pulse. It means that just after stopping of the driving pulse, the EUV emission corresponding to the excited states should also stop. From our earlier measurements in the optical range, however, it can be concluded that lifetimes of such plasmas exceed a time duration of the driving pulse even two orders of magnitude. Hence, it can be expected that the time duration of the EUV emission can be also significantly longer than the irradiation time. In this work, EUV-induced, low-temperature helium (He), krypton, and xenon plasmas were investigated. EUV emission from these plasmas was studied, using a specially prepared detection system, allowing for time-resolved measurements, in selected spectral ranges. The detection system was based on a paraboloidal collector and a semiconductor photodiode, sensitive for the EUV photons. For spectral selection, the corresponding filters or multilayer mirrors were employed. In most cases, the time duration of the EUV emission was significantly longer than the driving EUV pulse. In case of He plasmas, the emission corresponding to excited atoms was detected even hundreds of nanoseconds after the irradiation. It was also shown that the corresponding time profiles depended on densities of gases to be ionized.

scholarly journals Time-resolved measurements of extreme ultraviolet (EUV) emission, from EUV-induced He, Ne, and Ar plasmas

2019 ◽  
Vol 37 (01) ◽  
pp. 49-54 ◽  
Author(s):  
A. Bartnik ◽  
H. Fiedorowicz ◽  
P. Wachulak ◽  
T. Fok
Keyword(s):  
Low Temperature ◽  
Extreme Ultraviolet ◽  
Detection System ◽  
Time Duration ◽  
Time Resolved ◽  
Time Profiles ◽  
Euv Emission ◽  
Order Of Magnitude ◽  
Low Temperature Plasmas ◽  
Time Resolved Measurements

AbstractIrradiation of gases with intense pulses of extreme ultraviolet (EUV) can result in the formation of low-temperature plasmas. During the time of irradiation, various non-thermal processes driven by the EUV photons and photoelectrons take place, leading to the creation of excited states of atoms and ions. Fast relaxation of these states should result in EUV emission within a time comparable to the driving EUV pulse. On the other hand, from our earlier works, a time duration of the emission in an optical range is over an order of magnitude longer. It can be thus expected that the time of EUV emission can be also relatively long. In this work, time-resolved measurements of the EUV emission from low-temperature plasmas induced in He, Ne, and Ar gases were performed. Due to a low intensity of the emitted radiation, a specially prepared detection system, based on an EUV collector and an EUV sensitive photodiode, was employed. In all cases, a time duration of the EUV emission was much longer compared with the driving EUV pulse. Time profiles of the corresponding signals were specific for particular gases. In case of He and Ne plasmas, these time profiles varied with initial densities of gases to be ionized. The corresponding dependence was especially visible in case of plasmas induced in helium. In case of Ar plasmas, such dependence was not revealed.

scholarly journals Temporal measurements of extreme ultraviolet (EUV) emission, from low temperature, EUV-induced plasmas

2018 ◽  
Vol 36 (3) ◽  
pp. 286-292 ◽  
Author(s):  
A. Bartnik ◽  
H. Fiedorowicz ◽  
P. Wachulak ◽  
T. Fok
Keyword(s):  
Low Temperature ◽  
Extreme Ultraviolet ◽  
Detection System ◽  
Grazing Incidence ◽  
Euv Emission ◽  
Multiply Charged ◽  
Low Temperature Plasmas ◽  
Charged Ions ◽  
Different Gases ◽  
Selection Of

AbstractIn this work, extreme ultraviolet (EUV) emission, from EUV induced, low-temperature microplasmas, were investigated. To perform temporal measurements of the EUV pulses of low intensity, in a medium vacuum, under the pressure of the order of 0.1–0.01 mbar a special detection system was prepared. The system was based on an EUV collector and a semiconductor detector, sensitive for the EUV photons. The collector consisted of two identical grazing incidence, paraboloidal mirrors, and allowed to focus a part of the radiation emitted from the microplasma onto the detector surface. An absorption filter, mounted between the collector and the detector, allowed for selection of an interesting wavelength range. Plasmas were created by irradiation of small portions of gases, injected into the vacuum chamber, using a laser produced plasma EUV source. Three gases were used for the EUV induced plasma formation: neon, krypton, and xenon. Low-temperature plasmas, created in these gases, contained multiply charged ions, emitting radiation in similar wavelength ranges. Two detectors, AXUV20HS1 and AXUVHS5, were used for the measurements. It was shown that differences between the corresponding signal profiles, obtained using both detectors, were not very significant. Moreover, it was demonstrated that the duration of the EUV emission from plasmas, created in different gases, were comparable with the duration of the driving EUV pulse. The longest EUV emission was observed for Kr plasmas, approximately 1.5 times the full width half maximum of the driving EUV pulse.

scholarly journals Low-temperature plasmas induced in nitrogen by extreme ultraviolet (EUV) pulses

2018 ◽  
Vol 36 (1) ◽  
pp. 76-83 ◽  
Author(s):  
A. Bartnik ◽  
W. Skrzeczanowski ◽  
H. Fiedorowicz ◽  
P. Wachulak ◽  
T. Fok
Keyword(s):  
Low Temperature ◽  
Extreme Ultraviolet ◽  
High Energy ◽  
Molecular Ions ◽  
Molecular Spectra ◽  
Essential Difference ◽  
Time Resolved ◽  
Wide Wavelength Range ◽  
Low Temperature Plasmas ◽  
Spectral Ranges

AbstractIn this work, a comparative study of low-temperature plasmas, induced in a gaseous nitrogen by photoionization of the gas using two different irradiation systems, was performed. Both systems were based on laser-produced Xe plasmas, emitting intense extreme ultraviolet (EUV) radiation pulses in a wide wavelength range. The essential difference between the systems concerned formation of the EUV beam. The first one utilized a dedicated ellipsoidal mirror for collecting and focusing of the EUV radiation. This way a high radiation fluence could be obtained for ionization of the N2 gas injected into the vacuum chamber. The second system did not contain any EUV collector. In this case, the nitrogen to be ionized was injected into the vicinity of the Xe plasma. In both cases, energies of emitted photons were sufficient for dissociative ionization, ionization of atoms or even ions. The resulting photoelectrons had also sufficiently high energy for further ionizations or excitations. Low-temperature plasmas, created this way, were investigated by spectral measurements in the EUV, ultraviolet (UV) and visible (VIS) spectral ranges. Time-resolved UV/VIS spectra, corresponding to single-charged ions, molecules, and molecular ions, were recorded. Numerical simulations of the molecular spectra were performed allowing one to estimate vibrational and rotational temperatures of plasmas created using both irradiation systems.

Temperature Dependent and Time Resolved Optical Studies of Single Quantum Wells Produced by Interrupted Growth MBE

1986 ◽  
Vol 77 ◽  
Author(s):  
B. S. Elman ◽  
Emil S. Koteles ◽  
C. Jagannath ◽  
Y. J. Chen ◽  
S. Charbonneau ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Single Quantum ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Molecular Beam Epitaxial ◽  
Decay Times ◽  
Higher Temperature ◽  
The Individual ◽  
Molecular Beam Epitaxial Growth

ABSTRACTMultiple peaks, recently observed in the low temperature photoluminescence (PL) spectra of GaAs/AlGaAs single quantum wells fabricated by momentarily interrupting the molecular beam epitaxial growth between adjacent but different semiconductor layers, have been interpreted as originating within smooth regions in the quantum well layer differing in width by exactly one monolayer. We have observed similar structure in similarly grown samples but find that low temperature PL can be misleading. However, higher temperature PL or PL excitation spectroscopy do provide unambiguous evidence for the model of interface smoothing due to growth interruption. Further, time-resolved spectra yield decay times of the individual peaks which are consistent with this idea.

Time-resolved photoluminescence studies of InGaN/GaN multiple quantum wells

1997 ◽  
Vol 2 ◽  
Author(s):  
J. Allègre ◽  
P. Lefebvre ◽  
S. Juillaguet ◽  
W. Knap ◽  
J. Camassel ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Multiple Quantum Well ◽  
Stimulated Emission ◽  
Multiple Quantum ◽  
Nitrogen Laser ◽  
Energy Position ◽  
Blue Band ◽  
Time Resolved ◽  
Decay Times

We report both cw and time resolved optical investigations performed on an InGaN/GaN multiple quantum well grown by MOVPE on <0001>-oriented sapphire substrate. At low temperature we find a strong “blue” luminescence band, of which energy position corresponds well with the wavelength of stimulated emission when excited with a nitrogen laser. We show that this PL band appears systematically red-shifted with respect to the QWs features, which supports a standard picture of fluctuations of the indium composition. Coming to the time-resolved data, we find at low temperature at least two “blue” band components which are both associated with long decay times (up to 4-5 ns at 8K). The decay time is temperature dependent and, when rising the temperature, the recombination rate increases. At room temperature, we reach typical values in the range ~100 to 500 ps.

scholarly journals Ферстеровский резонансный перенос энергии с участием светлых и темных экситонов в массивах эпитаксиальных квантовых точек CdSe/ZnSe

2018 ◽  
Vol 60 (8) ◽  
pp. 1575
Author(s):  
Т.Н. Михайлов ◽  
Е.А. Европейцев ◽  
К.Г. Беляев ◽  
A.A. Торопов ◽  
A.В. Родина ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excited States ◽  
Energy Transfer Process ◽  
Dipole Interaction ◽  
Energy Transfer Mechanism ◽  
Time Resolved ◽  
Decay Times ◽  
Förster Energy Transfer ◽  
Excitonic States ◽  
Time Resolved Photoluminescence

AbstractUsing time-resolved photoluminescence (PL) spectroscopy, we establish the presence of the Förster energy transfer mechanism between two arrays of epitaxial CdSe/ZnSe quantum dots (QDs) of different sizes. The mechanism operates through dipole–dipole interaction between ground excitonic states of the smaller QDs and excited states of the larger QDs. The dependence of energy transfer efficiency on the width of barrier separating the QD insets is shown to be in line with the Förster mechanism. The temperature dependence of the PL decay times and PL intensity suggests the involvement of dark excitons in the energy transfer process.

Controlling Growth of InAs/GaAs Self-Assembled Quantum Dots to Give 1.3 μm Room Temperature Emission

1999 ◽  
Vol 571 ◽  
Author(s):  
Surama Malik ◽  
Philip Siverns ◽  
David Childs ◽  
Christine Roberts ◽  
Jean-Michel Hartmann ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Excited States ◽  
Room Temperature ◽  
Growth Parameters ◽  
High Growth ◽  
Growth Conditions ◽  
Time Resolved ◽  
Confining Potential ◽  
Decay Times ◽  
Self Assembled

ABSTRACTWe have investigated the extent to which the emission wavelength of self-assembled InAs/GaAs quantum dots can be controlled by growth parameters using conventional solid source MBE. Changing from conventionally high growth rates to a very low growth rate (LGR) and a relatively high substrate temperature, tunes the photoluminescence (PL) emission from 1.1 μm to 1.3 μm at room temperature. Atomic force micrographs obtained from uncapped samples reveal that these LGRQDs are larger, lower in density and extremely uniform in size. The improved size uniformity is reflected in the reduction of the PL linewidth from 78 meV to 22 meV. Under conditions of high excitation, emission from the ground and two excited states each separated by ∼70 meV is observed. This implies a parabolic confining potential. Time resolved photoluminescence (TRPL) measurements of dots grown under the various growth conditions yield radiative lifetimes which reflect the depth of the confining potential. A comparison of the decay times measured for the excited states show that the relaxation of carriers within the dots cannot be ascribed to phonon effects.

The promises and perfidy of cryomicroscopy and analysis

1994 ◽  
Vol 52 ◽  
pp. 382-383
Author(s):  
Patrick Echlin
Keyword(s):  
Low Temperature ◽  
High Energy ◽  
Short Paper ◽  
List Type ◽  
Time Resolved ◽  
Energy Beam ◽  
Cellular Analysis ◽  
Dissolved Ions ◽  
Embedding Medium ◽  
Low Temperature Microscopy

The unusual title of this short paper and its accompanying tutorial is deliberate, because the intent is to investigate the effectiveness of low temperature microscopy and analysis as one of the more significant elements of the less interventionist procedures we can use to prepare, examine and analyse hydrated and organic materials in high energy beam instruments. The promises offered by all these procedures are well rehearsed and the litany of petitions and responses may be enunciated in the following mantra.Vitrified water can form the perfect embedding medium for bio-organic samples.Frozen samples provide an important, but not exclusive, milieu for the in situ sub-cellular analysis of the dissolved ions and electrolytes whose activities are central to living processes.The rapid conversion of liquids to solids provides a means of arresting dynamic processes and permits resolution of the time resolved interactions between water and suspended and dissolved materials.The low temperature environment necessary for cryomicroscopy and analysis, diminish, but alas do not prevent, the deleterious side effects of ionizing radiation.Sample contamination is virtually eliminated.

Solvent Dependence of Structural Dynamics and Spin-flip Processes in 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (ortho-3CzBN)

2020 ◽  
Author(s):  
Masaki Saigo ◽  
Kiyoshi Miyata ◽  
Hajime Nakanotani ◽  
Chihaya Adachi ◽  
Ken Onda
Keyword(s):  
Dft Calculations ◽  
Excited States ◽  
Structural Changes ◽  
Photophysical Properties ◽  
Delayed Fluorescence ◽  
Time Resolved ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Solvent Dependence ◽  
Acetonitrile Solutions

We have investigated the solvent-dependence of structural changes along with intersystem crossing of a thermally activated delayed fluorescence (TADF) molecule, 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (o-3CzBN), in toluene, tetrahydrofuran, and acetonitrile solutions using time-resolved infrared (TR-IR) spectroscopy and DFT calculations. We found that the geometries of the S1 and T1 states are very similar in all solvents though the photophysical properties mostly depend on the solvent. In addition, the time-dependent DFT calculations based on these geometries suggested that the thermally activated delayed fluorescence process of o-3CzBN is governed more by the higher-lying excited states than by the structural changes in the excited states.<br>

The Character of Low-Lying Excited States of Mixed-Ligand Metal Carbonyls. TD-DFT and CASSCF/CASPT2 Study of [W(CO)4L] (L = ethylenediamine, N,N'-dialkyl-1,4-diazabutadiene) and [W(CO)5L] (L = pyridine, 4-cyanopyridine)

2003 ◽  
Vol 68 (1) ◽  
pp. 89-104 ◽  
Author(s):  
Stanislav Záliš ◽  
Antonín Vlček ◽  
Chantal Daniel
Keyword(s):  
Excited States ◽  
Substitution Effect ◽  
Electronic Transitions ◽  
Ligand Field ◽  
Metal Carbonyls ◽  
Electron Density Redistribution ◽  
Time Resolved ◽  
Model Complex ◽  
Td Dft ◽  
Time Resolved Infrared Spectroscopy

This contribution presents the results of the TD-DFT and CASSCF/CASPT2 calculations on [W(CO)4(MeDAB)] (MeDAB = N,N'-dimethyl-1,4-diazabutadiene), [W(CO)4(en)] (en = ethylenediamine), [W(CO)5(py)] (py = pyridine) and [W(CO)5(CNpy)] (CNpy = 4-cyanopyridine) complexes. Contrary to the textbook interpretation, calculations on the model complex [W(CO)4(MeDAB)] and [W(CO)5(CNpy)] show that the lowest W→MeDAB and W→CNpy MLCT excited states are immediately followed in energy by several W→CO MLCT states, instead of ligand-field (LF) states. The lowest-lying excited states of [W(CO)4(en)] system were characterized as W(COeq)2→COax CT excitations, which involve a remarkable electron density redistribution between axial and equatorial CO ligands. [W(CO)5(py)] possesses closely-lying W→CO and W→py MLCT excited states. The calculated energies of these states are sensitive to the computational methodology used and can be easily influenced by a substitution effect. The calculated shifts of [W(CO)4(en)] stretching CO frequencies due to excitation are in agreement with picosecond time-resolved infrared spectroscopy experiments and confirm the occurrence of low-lying M→CO MLCT transitions. No LF electronic transitions were found for either of the complexes studied in the region up to 4 eV.

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