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Richard E Russo - One of the best experts on this subject based on the ideXlab platform.
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liquid sampling atmospheric pressure glow discharge as a secondary excitation source assessment of plasma characteristics
2014Co-Authors: Richard E Russo, Benjamin T Manard, Jhanis J Gonzalez, Arnab Sarkar, Meirong Dong, Jose Chirinos, Xianglei Mao, Kenneth R MarcusAbstract:Abstract The liquid sampling-atmospheric pressure glow discharge (LS-APGD) has been assessed as a secondary excitation source with a parametric evaluation regarding carrier gas flow rate, applied current, and electrode distance. With this parametric evaluation, plasma optical emission was monitored in order to obtain a fundamental understanding with regards to rotational temperature (Trot), excitation temperature (Texc), Electron Number density (ne), and plasma robustness. Incentive for these studies is not only for a greater overall fundamental knowledge of the APGD, but also in instrumenting a secondary excitation/ionization source following laser ablation (LA). Rotational temperatures were determined through experimentally fitting of the N2 and OH molecular emission bands while atomic excitation temperatures were calculated using a Boltzmann distribution of He and Mg atomic lines. The rotational and excitation temperatures were determined to be ~ 1000 K and ~ 2700 K respectively. Electron Number density was calculated to be on the order of ~ 3 × 1015 cm− 3 utilizing Stark broadening effects of the Hα line of the Balmer series and a He I transition. In addition, those diagnostics were performed introducing magnesium (by solution feed and laser ablation) into the plasma in order to determine any perturbation under heavy matrix sampling. The so-called plasma robustness factor, derived by monitoring Mg II/Mg I emission ratios, is also employed as a reflection of potential perturbations in microplasma energetics across the various operation conditions and sample loadings. While truly a miniaturized source (
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laser induced shockwave propagation from ablation in a cavity
2006Co-Authors: Xianzhong Zeng, R Greif, Richard E RussoAbstract:The propagation of laser-induced shockwaves from ablation inside of cavities was determined from time-resolved shadowgraph images. The temperature and Electron Number density of the laser-induced plasma was determined from spectroscopic measurements. These properties were compared to those for laser ablation on the flat surface under the same energy and background gas condition. A theoretical model was proposed to determine the amount of energy and vaporized mass stored in the vapor plume based on these measurements.
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experimental investigation of ablation efficiency and plasma expansion during femtosecond and nanosecond laser ablation of silicon
2005Co-Authors: Xianzhong Zeng, Xianglei Mao, R Greif, Richard E RussoAbstract:Femtosecond laser (Ti:sapphire, 100 fs pulse duration) ablation of silicon in air was compared with nanosecond laser (Nd:YAG, 3 ns pulse duration) ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse Number. For the same Number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and Electron Number density of the laser-induced plasma were determined from spectroscopic measurements. The Electron Number density and temperature of fs-induced plasmas decreased faster than ns-induced plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions were compared.
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plasma diagnostics during laser ablation in a cavity
2003Co-Authors: Xianzhong Zeng, R Greif, Richard E RussoAbstract:Abstract The formation of a laser-induced plasma in a cavity and the effects of a cavity on the ablation process were investigated. Cavities were fabricated in fused silica with equal depths and variable diameters to provide aspect ratios (depth/diameter) of 1, 3 and 6. The temperature and Electron Number density of the pulsed laser-induced plasma in the cavities were determined from spectroscopic measurements. Reflection and confinement effects by the cavity walls and plasma shielding were discussed to explain increased temperature and Electron Number density with increasing cavity aspect ratio. The temporal variations of the plasma temperature and Electron Number density sharply decreased inside the cavity. An adiabatic expansion model was not suitable for the laser-induced plasma in the cavity because plasma wall interactions were not included. Properties of laser-induced plasmas in the cavities and on a flat surface were compared.
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imaging femtosecond laser induced Electronic excitation in glass
2003Co-Authors: Richard E RussoAbstract:While substantial progress has been achieved in understanding laser ablation on the nanosecond and picosecond time scales, it remains a considerable challenge to elucidate the underlying mechanisms during femtosecond laser material interactions. We present experimental observations of Electronic excitation inside a wide band gap glass during single femtosecond laser pulse (100 fs, 800 nm) irradiation. Using a femtosecond time-resolved imaging technique, we measured the evolution of a laser-induced Electronic plasma inside the glass and calculated the Electron Number density to be on the order of 1019 cm−3.
N Konjevic - One of the best experts on this subject based on the ideXlab platform.
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stark width and shift for Electron Number density diagnostics of low temperature plasma application to silicon laser induced breakdown spectroscopy
2017Co-Authors: M Ivkovic, N KonjevicAbstract:Abstract In this work we summarize, analyze and critically evaluate experimental procedures and results of LIBS Electron Number density plasma characterization using as examples Stark broadened Si I and Si II line profiles. Selected publications are covering the time period from very beginning of silicon LIBS studies until the end of the year 2015. To perform the analysis of experimental LIBS data, the testing of available semiclassical theoretical Stark broadening parameters for Si I and Si II lines was accomplished first. This is followed by the description of experimental setups, results and details of experimental procedure relevant for the line shape analysis of spectral lines used for plasma characterization. Although most of results and conclusions of this analysis are related to the application of silicon lines for LIBS characterization they are of general importance and may be applied to other elements and different low-temperature plasma sources. The analysis of experimental procedures used for LIBS diagnostics from emission profiles of non-hydrogenic spectral lines is carried out in the following order: the influence of laser ablation and crater formation, spatial and temporal plasma observation, line self-absorption and experimental profile deconvolution, the contribution of ion broadening in comparison with Electron impacts contributions to the line width in case of neutral atom line and some other aspects of line shape analysis are considered. The application of Stark shift for LIBS diagnostics is demonstrated and discussed. Finally, the recommendations for an improvement of experimental procedures for LIBS Electron Number density plasma characterization are offered.
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hydrogen balmer lines for low Electron Number density plasma diagnostics
2012Co-Authors: N Konjevic, M Ivkovic, N M SakanAbstract:Abstract We present an analysis of the procedure for plasma Electron Number density, N e , diagnostics based on the comparison of theoretical and experimental shape or width of hydrogen Balmer lines. Low N e diagnostics, requiring an extension of available theoretical Stark broadening data tables was examined first. The difficulties encountered during experimental line profile analysis at low N e are discussed and appropriate procedures suggested. The widely adopted deconvolution of experimental profile by fitting with a Voigt function is examined and it is shown that this deconvolution introduces large systematic error in Stark width determination. This uncertainty can be decreased but never completely avoided by fixing the Gaussian part of the Voigt function. Simple formulas of satisfactory accuracy for deconvolution at the half width of experimental profile were investigated and their application recommended. The contribution of Van der Waals broadening to the experimental profile is examined and the correction for its contribution discussed. Approximate and reliable formulas for the evaluation of N e from the Stark width were critically evaluated. To estimate the applicability of different sets of theoretical data for N e diagnostics, a comparison of theory versus experiments was carried out and best data tables were recommended. For low N e diagnostics the application of higher members of Balmer series is advised whenever possible.
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a simple line shape technique for Electron Number density diagnostics of helium and helium seeded plasmas
2010Co-Authors: M Ivkovic, Manuel A Gonzalez, S Jovicevic, M A Gigosos, N KonjevicAbstract:Abstract The results of an experimental study of the He I 447.1 nm line and its forbidden component at high Electron Number density are presented and compared with profiles calculated using computer simulation method. Michelson interferometer at 632.8 nm was used to measure plasma Electron Number density in the range (1–7) × 10 23 m − 3 while Electron temperatures for the same experimental conditions in the range of 25 000 K to 35 000 K were determined using several spectroscopic techniques. The agreement of experimental overall line shape with computer simulation results is within 10% of what is well within theoretical and experimental uncertainty. This favorable comparison enabled the development of a simple approximate formula for the evaluation of Electron Number density from the measurement of wavelength separation between peaks of allowed and forbidden lines. This technique of plasma diagnostics is not sensitive to the presence of self-absorption of strong He I allowed line. The derivation of approximate formula with estimated accuracy of 15% was followed by detailed comparison with other experimental and theoretical data.
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a program for the evaluation of Electron Number density from experimental hydrogen balmer beta line profiles
2002Co-Authors: R žikic, Manuel A Gonzalez, M Ivkovic, M A Gigosos, N KonjevicAbstract:Abstract A program for the determination of plasma Electron Number density, 1020≤(Ne)≤1023 m−3, from the comparison of experimental and theoretical hydrogen Balmer beta (Hβ) line profiles is described in detail. Three theoretical data sets (one set is calculated within the framework of this paper) are included with the program and may be selected as a user's choice. Apart from Ne determination from the comparison of the whole experimental and theoretical profiles, this program offers a fast estimation of Ne from the halfwidth of the experimental line shape. If necessary, certain parts of the experimental profile may be neglected in the procedure of comparison with theory. This possibility enables the use of noisy line shape recordings for Ne determination. The Hβ asymmetry study may be carried out by generating the difference between experimental and best-fitted theoretical line profiles.
E. Odelstad - One of the best experts on this subject based on the ideXlab platform.
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the evolution of the Electron Number density in the coma of comet 67p at the location of rosetta from 2015 november through 2016 march
2019Co-Authors: E. Vigren, M. Galand, Pierre Henri, E. Odelstad, M. Rubin, Niklas J T Edberg, Anders Eriksson, Fredrik L Johansson, Xavier VallièresAbstract:A comet ionospheric model assuming the plasma to move radially outward with the same bulk speed as the neutral gas and not being subject to severe reduction through dissociative recombination has previously been tested in a series of case studies associated with the Rosetta mission at comet 67P/Churyumov-Gerasimenko. It has been found that at low activity and within several tens of km from the nucleus such models (which originally were developed for such conditions) generally work well in reproducing observed Electron Number densities, in particular when plasma production through both photoionization and Electron-impact ionization is taken into account. Near perihelion, case studies have, on the contrary, showed that applying similar assumptions overestimates the observed Electron Number densities at the location of Rosetta. Here we compare ROSINA/COPS driven model results with RPC/MIP derived Electron Number densities for an extended time period (2015 November through 2016 March) during the post-perihelion phase with southern summer/spring. We observe a gradual transition from a state when the model grossly overestimates (by more than a factor of 10) the observations to being in reasonable agreement during 2016 March.
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The Evolution of the Electron Number Density in the Coma of Comet 67P at the Location of Rosetta from 2015 November through 2016 March
2019Co-Authors: E. Vigren, N. Edberg, A. Eriksson, M. Galand, Pierre Henri, F. Johansson, E. Odelstad, M. Rubin, Xavier VallièresAbstract:A comet ionospheric model assuming the plasma moves radially outward with the same bulk speed as the neutral gas and not being subject to severe reduction through dissociative recombination has previously been tested in a series of case studies associated with the Rosetta mission at comet 67P/Churyumov-Gerasimenko. It has been found that at low activity and within several tens of kilometers from the nucleus such models (which originally were developed for such conditions) generally work well in reproducing observed Electron Number densities, in particular when plasma production through both photoionization and Electron-impact ionization is taken into account. Near perihelion, case studies have, on the contrary, shown that applying similar assumptions overestimates the observed Electron Number densities at the location of Rosetta. Here we compare Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Comet Pressure sensor-driven model results with Rosetta Plasma Consortium/Mutual Impedance Probe-derived Electron Number densities for an extended time period (2015 November through 2016 March) during the postperihelion phase with southern summer/spring. We observe a gradual transition from a state when the model grossly overestimates (by more than a factor of 10) the observations to being in reasonable agreement during 2016 March.
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the evolution of the Electron Number density in the coma of comet 67p at the location of rosetta from 2015 november through 2016 march
2019Co-Authors: E. Vigren, M. Galand, Pierre Henri, E. Odelstad, M. Rubin, Niklas J T Edberg, Anders Eriksson, Fredrik L Johansson, Xavier VallièresAbstract:A comet ionospheric model assuming the plasma moves radially outward with the same bulk speed as the neutral gas and not being subject to severe reduction through dissociative recombination has pre ...
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model observation comparisons of Electron Number densities in the coma of 67p churyumov gerasimenko during 2015 january
2016Co-Authors: E. Vigren, M. Galand, E. Odelstad, Kathrin Altwegg, Niklas J T Edberg, Anders Eriksson, P Henri, Fredrik JohanssonAbstract:During 2015 January 9–11, at a heliocentric distance of ~2.58–2.57 au, the ESA Rosetta spacecraft resided at a cometocentric distance of ~28 km from the nucleus of comet 67P/Churyumov–Gerasimenko, sweeping the terminator at northern latitudes of 43°N–58°N. Measurements by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Comet Pressure Sensor (ROSINA/COPS) provided neutral Number densities. We have computed modeled Electron Number densities using the neutral Number densities as input into a Field Free Chemistry Free model, assuming H2O dominance and ion-Electron pair formation by photoionization only. A good agreement (typically within 25%) is found between the modeled Electron Number densities and those observed from measurements by the Mutual Impedance Probe (RPC/MIP) and the Langmuir Probe (RPC/LAP), both being subsystems of the Rosetta Plasma Consortium. This indicates that ions along the nucleus-spacecraft line were strongly coupled to the neutrals, moving radially outward with about the same speed. Such a statement, we propose, can be further tested by observations of H3O+/H2O+ Number density ratios and associated comparisons with model results.
M A Blanco - One of the best experts on this subject based on the ideXlab platform.
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a connection between domain averaged fermi hole orbitals and Electron Number distribution functions in real space
2009Co-Authors: E Francisco, Martin A Pendas, M A BlancoAbstract:We show in this article how for single-determinant wave functions the one-Electron functions derived from the diagonalization of the Fermi hole, averaged over an arbitrary domain Ω of real space, and expressed in terms of the occupied canonical orbitals, describe coarse-grained statistically independent Electrons. With these domain-averaged Fermi hole (DAFH) orbitals, the full Electron Number distribution function (EDF) is given by a simple product of one-Electron events. This useful property follows from the simultaneous orthogonality of the DAFH orbitals in Ω, Ω′=R3−Ω, and R3. We also show how the interfragment (shared Electron) delocalization index, δΩ,Ω′, transforms into a sum of one-Electron DAFH contributions. Description of chemical bonding in terms of DAFH orbitals provides a vivid picture relating bonding and delocalization in real space. DAFH and EDF analyses are performed on several test systems to illustrate the close relationship between both concepts. Finally, these analyses clearly prove ho...
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edf computing Electron Number probability distribution functions in real space from molecular wave functions
2008Co-Authors: E Francisco, Martin A Pendas, M A BlancoAbstract:Given an N -Electron molecule and an exhaustive partition of the real space (R3R3) into m arbitrary regions Ω1,Ω2,…,ΩmΩ1,Ω2,…,Ωm (⋃i=1mΩi=R3), the edf program computes all the probabilities P(n1,n2,…,nm)P(n1,n2,…,nm) of having exactly n1n1 Electrons in Ω1Ω1, n2n2 Electrons in Ω2,…, and nmnm Electrons (n1+n2+⋯+nm=Nn1+n2+⋯+nm=N) in ΩmΩm. Each ΩiΩi may correspond to a single basin (atomic domain) or several such basins (functional group). In the later case, each atomic domain must belong to a single ΩiΩi. The program can manage both single- and multi-determinant wave functions which are read in from an aimpac-like wave function description (.wfn) file (T.A. Keith et al., The AIMPAC95 programs, http://www.chemistry.mcmaster.ca/aimpac, 1995). For multi-determinantal wave functions a generalization of the original .wfn file has been introduced. The new format is completely backwards compatible, adding to the previous structure a description of the configuration interaction (CI) coefficients and the determinants of correlated wave functions. Besides the .wfn file, edf only needs the overlap integrals over all the atomic domains between the molecular orbitals (MO). After the P(n1,n2,…,nm)P(n1,n2,…,nm) probabilities are computed, edf obtains from them several magnitudes relevant to chemical bonding theory, such as average Electronic populations and localization/delocalization indices. Regarding spin, edf may be used in two ways: with or without a splitting of the P(n1,n2,…,nm)P(n1,n2,…,nm) probabilities into α and β spin components. Program summary Program title: edf Catalogue identifier: AEAJ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAJ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 5387 No. of bytes in distributed program, including test data, etc.: 52 381 Distribution format: tar.gz Programming language: Fortran 77 Computer: 2.80 GHz Intel Pentium IV CPU Operating system: GNU/Linux RAM: 55 992 KB Word size: 32 bits Classification: 2.7 External routines: Netlib Nature of problem: Let us have an N-Electron molecule and define an exhaustive partition of the physical space into m three-dimensional regions. The edf program computes the probabilities P(n1,n2,…,nm)≡P({np})P(n1,n2,…,nm)≡P({np}) of all possible allocations of n1n1 Electrons to Ω1Ω1, n2n2 Electrons to Ω2,…, and nmnm Electrons to Ωm,{np}Ωm,{np} being integers. Solution method: Let us assume that the N -Electron molecular wave function, Ψ(1,N)Ψ(1,N), is a linear combination of M Slater determinants, Ψ(1,N)=∑rMCrψr(1,N). Calling SΩkrs the overlap matrix over the 3D region ΩkΩk between the (real) molecular spin-orbitals (MSO) in ψr(χ1r,…χNr) and the MSOs in ψs,(χ1s,…,χNs), edf finds all the P({np})P({np})'s by solving the linear system equation(1) ∑{np}{∏kmtknk}P({np})=∑r,sMCrCsdet[∑kmtkSΩkrs], where tm=1tm=1 and t1,…,tm−1t1,…,tm−1 are arbitrary real Numbers. Restrictions: The Number of {np}{np} sets grows very fast with m and N, so that the dimension of the linear system (1) soon becomes very large. Moreover, the computer time required to obtain the determinants in the second member of Eq. (1) scales quadratically with M. These two facts limit the applicability of the method to relatively small molecules. Unusual features: Most of the real variables are of precision real*16. Running time: 0.030, 2.010, and 0.620 seconds for Test examples 1, 2, and 3, respectively. References: [1] A. Martin Pendas, E. Francisco, M.A. Blanco, Faraday Discuss. 135 (2007) 423–438. [2] A. Martin Pendas, E. Francisco, M.A. Blanco, J. Phys. Chem. A 111 (2007) 1084–1090. [3] A. Martin Pendas, E. Francisco, M.A. Blanco, Phys. Chem. Chem. Phys. 9 (2007) 1087–1092. [4] E. Francisco, A. Martin Pendas, M.A. Blanco, J. Chem. Phys. 126 (2007) 094102. [5] A. Martin Pendas, E. Francisco, M.A. Blanco, C. Gatti, Chemistry: A European Journal 113 (2007) 9362–9371.
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Electron Number probability distributions for correlated wave functions
2007Co-Authors: E Francisco, Martin A Pendas, M A BlancoAbstract:Efficient formulas for computing the probability of finding exactly an integer Number of Electrons in an arbitrarily chosen volume are only known for single-determinant wave functions [E. Cances et al., Theor. Chem. Acc. 111, 373 (2004)]. In this article, an algebraic method is presented that extends these formulas to the case of multideterminant wave functions and any Number of disjoint volumes. The derived expressions are applied to compute the probabilities within the atomic domains derived from the space partitioning based on the quantum theory of atoms in molecules. Results for a series of test molecules are presented, paying particular attention to the effects of Electron correlation and of some numerical approximations on the computed probabilities.
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pauling resonant structures in real space through Electron Number probability distributions
2007Co-Authors: Martin A Pendas, E Francisco, M A BlancoAbstract:A general hierarchy of the coarsed−grained Electron probability distributions induced by exhaustive partitions of the physical space is presented. It is argued that when the space is partitioned into atomic regions the consideration of these distributions may provide a first step toward an orbital invariant treatment of resonant structures. We also show that, in this case, the total molecular energy and its components may be partitioned into structure contributions, providing a fruitful extension of the recently developed interacting quantum atoms approach (J. Chem. Theory Comput. 2005, 1, 1096). The above ideas are explored in the hydrogen molecule, where a complete statistical and energetic decomposition into covalent and ionic terms is presented.
Mark A. Cappelli - One of the best experts on this subject based on the ideXlab platform.
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laser absorption measurements of Electron density in nanosecond scale atmospheric pressure pulsed plasmas
2021Co-Authors: T Yong, Ahmed I Abdalla, Mark A. CappelliAbstract:We report on time-resolved measurements of Electron Number density by continuous-wave laser absorption in a low-energy nanosecond-scale laser-produced spark in atmospheric pressure air. Laser absorption is a result of free-free and bound-free Electron excitation, with the absorption coefficient modeled and evaluated using estimates of the time-variation in Electron temperature and probe laser absorption path length. Plasma Electron Number densities are determined to be as high as n e = 7 × 10 19 cm−3 and decay to 1 / e of their peak values over a period of about 50 ns following plasma formation using a 20 mJ, 10 ns pulse width frequency-doubled Nd:YAG laser. The measured plasma densities at later times are shown to be in reasonable agreement with Stark broadening measurements of the 3s[ 5 S o]-3p[ 5 P] Electronic transition in atomic oxygen at 777 nm. This study provides support for the use of such continuous wave laser absorption for time resolved Electron density measurements in low energy spark discharges in air, provided that an estimate of the Electron temperature and laser path length can be made by accompanying diagnostics.
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Electron Number density measurements from the frequency shift of a plasma defect state in a one dimensional photonic crystal
2019Co-Authors: Fabio Righetti, Benjamin Wang, David Biggs, Mark A. CappelliAbstract:We describe the use of a plasma-functionalized vacancy defect in a one-dimensional microwave photonic crystal to experimentally measure the Electron Number density of glow discharges at 5--40 torr. The photonic crystal consists of spaced alumina plates with a built-in void defect that breaks the repeating symmetry of the layers, resulting in narrow defect transmission peaks within relatively deep bandgaps. We exploit the sensitivity of the defect transmission at 28 GHz to varying plasma density to measure Electron Number densities as low as 2 × 109 cm−3. Defect energy shifts are proportional to plasma density, in reasonable agreement with theoretical predictions of photonic crystal performance. At higher discharge current densities and discharge pressure, we see a departure from the model predictions, largely attributable to the heating of the alumina structure, causing expansion and changes in the lattice parameter that counteract the effect of the increased plasma density on the defect state frequency.