Population Distribution Of Excited States Research Articles

Reconsideration of Temperature Determined by the Excited-State Population Distribution of Hydrogen Atoms Based on Tsallis Entropy and Its Statistics in Hydrogen Plasma in Non-Equilibrium State.

In non-equilibrium plasmas, the temperature cannot be uniquely determined unless the energy-distribution function is approximated as a Maxwell-Boltzmann distribution. To overcome this problem, we applied Tsallis statistics to determine the temperature with respect to the excited-state populations in non-equilibrium state hydrogen plasma, which enables the description of its entropy that obeys q-exponential population distribution in the non-equilibrium state. However, it is quite difficult to apply the q-exponential distribution because it is a self-consistent function that cannot be solved analytically. In this study, a self-consistent iterative scheme was adopted to calculate q-exponential distribution using the similar algorithm of the Hartree-Fock method. Results show that the excited-state population distribution based on Tsallis statistics well captures the non-equilibrium characteristics in the high-energy region, which is far from the equilibrium-Boltzmann distribution. The temperature was calculated using the partial derivative of entropy with respect to the mean energy based on Tsallis statistics and using the coefficient of q-exponential distribution. An analytical expression was derived and compared with Boltzmann statistics, and the distribution was discussed from the viewpoint of statistical physics.

Population Distribution of Excited States in Cs Electrodeless Discharge Lamp**Supported by the National Natural Science Foundation of China under Grant Nos 11074011 and 91436210.

We measure the intensity of fluorescence spectral lines of Cs atoms in an electrodeless discharge lamp from visible light to the near-infrared region of 400–1000 nm. To build an excited state Faraday anomalous dispersion optical filter, the population ratios between the excited states are calculated by rate equations and the spontaneous transition probabilities. The electrodeless discharge lamp with populations in the excited states can be used to realize the frequency stabilization reference for lasers at multiwavelength and the excited state Faraday anomalous dispersion optical filter for submarine communication applications in blue—green wavelengths to simplify the system.

Effect of Excited-State Structural Relaxation on Midgap Excitations in Co2+-Doped ZnO Quantum Dots

The unique midgap excited states of Co2+-doped ZnO quantum dots have given rise to new applications in photocatalysis, sensing, magneto-optics, and magnetoelectronics. However, the electronic characteristics of these midgap transitions are not fully understood, and the uncertain interplay between these transitions has led to disagreement in the literature. In this work, midgap excited states of Co2+-doped ZnO quantum dots are analyzed using linear response time-dependent density functional theory and the effective mass theory with a focus on the geometry relaxation in the donor-type photoionization excited state. Relaxation of the excited-state geometry lowers the charge-transfer transition energy to be in the vicinity of the prominent spin-allowed 4A2 → 4T1 Co2+ d–d transition that gives this material its characteristic color. For large quantum dots, the excited-state population distribution between this Co2+ d–d excited state and the charge-transfer excited state can be tuned by thermal energy, resultin...

Atomic population distribution of excited states in He electrodeless discharge lamp

Population ratios between excited states are measured to build the excited state Faraday anomalous dispersion optical filter (ESFADOF). We calculate these values between the excited states according to the spontaneous transition probabilities using rate equations and the measured intensities of fluorescence spectral lines of He atoms in an electrodeless discharge lamp in the visible spectral region from 350 to 730 nm. The electrodeless discharge lamp with populations in excited states can be used to realize the frequency stabilization reference of the laser frequency standard. This lamp can also build ESFADOFs for submarine communication application in the blue-green wavelength to simplify the system without the use of a pump laser.

Evaluation of Electron Energy Distribution Function in Microwave Discharge Plasmas by Spectroscopic Diagnostics with Collisional Radiative Model

The effect of the electron energy distribution function (EEDF) on the population distribution of excited states is investigated in He and Ar plasmas sustained by a 2.45 GHz microwave at a discharge pressure of 1–5 Torr. The EEDF is measured with a Langmuir probe by Druyvesteyn's method and used as the input parameter of the collisional-radiative (CR) model calculation. The calculated population density of the excited states is compared with the results of optical emission spectroscopic measurement. Reasonable agreement is found between them. It is also confirmed that the measured EEDFs was depleted at energies above the first excitation potential of the discharge gas atoms. When we assume a Maxwellian EEDF and calculate the population distribution of excited states of the argon plasma, we find a marked discrepancy between the populations of excited states observed experimentally and those calculated by the CR model, while a discrepancy for the helium plasma is also found but is less marked.

Numerical Bound State Electron Dynamics of Carbon Dioxide in the Strong-Field Regime

Time-dependent Hartree-Fock simulations for a linear triatomic molecule (CO(2)) interacting with a short IR (1.63 eV) three-cycle pulse reveal that the carrier-envelope shape and phase are the essential field parameters determining the bound state electron dynamics during and after the laser-molecule interaction. Analysis of the induced dipole oscillation reveals that the envelope shape (Gaussian or trapezoidal) controls the excited state population distribution. Varying the carrier envelope phase for each of the two pulse envelope shapes considerably changes the excited state populations. Increasing the electric field amplitude alters the relative populations of the excited states, generally exciting higher states. A windowed Fourier transform analysis of the dipole evolution during the laser pulse reveals the dynamics of state excitation and in particular state coupling as the laser intensity increases.

The excited-state population distribution of titanium atoms in A d.c. Argon plasma jet at atmospheric pressure

The distribution of excited-state titanium atoms in an argon plasma at atmospheric pressure has been studied by spectroscopic measurements. The upper levels of the argon atoms were found to be in equilibrium with the continuum; electron collisions are dominant for these levels and the Boltzmann temperature compared favorably with the LTE temperature obtained from the extrapolated electron density. The distribution of titanium atoms was found to be far from equilibrium. The temperature determined from the intensity ratios of titanium emission lines differs by a factor of more than two from the electron temperature obtained from argon emission-line data. The titanium data were corrected by using a modified diffusion model. The resulting electron temperature is within 14% of that determined from a Boltzmann plot of the argon emission lines. This study suggests a procedural method to use emission-line data of metal atoms in a low-temperature plasma to obtain a better estimate of the electron temperature and to predict other population densities for situations in which the energy separation of the excited state from the ionization level is sufficiently large so that radiation processes are dominant over excited-state depopulations.

A theoretical study of the influence of ambipolar diffusion on the population distribution of excited states in a plasma

The effect of charged particle diffusion on excitation temperature was investigated theoretically, assuming that the diffusion processes are ambipolar and that the charged particles return to the plasma in the form of ground state atoms, after recombination at the plasma boundary. An approximate expression was obtained by solving a set of balance equations for the excited state atom densities. It shows that, with increase of the plasma pressure, the excitation temperature rises and approaches the electron temperature. It was found also that, as the electron density increases, the diffusion effect on the excitation temperature diminishes. A criterion was obtained which should be satisfied so that the excitation temperature may be in agreement with the electron temperature. The theoretical results of this paper are in good agreement with experimental results.