S. M. Avdeev

Investigation of the conditions of efficient I*2 (342 nm) luminescence in a barrier discharge in a Kr-I2 mixture

The energy and spectral characteristics of a barrier discharge in a mixture of iodine vapor with krypton have been investigated theoretically and experimentally. The emission spectrum consists of the single I*2 molecular band D′ → A′ peaking at 342 nm, the iodine resonance line at 206.2 nm, and the group of bands corresponding to iodine emission. The highest intensity of the I*2 (342 nm) band was obtained at a mixture pressure near 450 Torr. A mean output power and an efficiency of 550 mW and 1.6%, respectively, have been achieved. It is shown that, for the I2 barrier-discharge excilamp, the homogeneous, rather than filamentary form of discharge glow is optimal from the viewpoint of the highest mean output power. The maximal calculated value of the emission efficiency for the 342-nm band was 5%. The main processes determining energy losses in plasma have been found, and ways to increase the efficiency of emission in the D′ → A′ band of the I*2 molecule have been proposed.

Barrier-discharge excilamp on a mixture of krypton and molecular bromine and chlorine

Spectral and energy characteristics of a barrier-discharge excilamp on a mixture of krypton with bromine and chlorine molecules that emits in the range 200–300 nm are presented. The radiation spectrum contains the bands of the B → X transitions of the KrCl* (222 nm) and KrBr* (207 nm) molecules and the band of the D′ → A′ transition of the Br*2 molecule (291 nm). It is demonstrated that the bromine content must be higher than the chlorine content in the triple (Kr−Cl2−Br2) mixtures that are optimal with respect to the radiant power. A radiant power of 0.7 W and an efficiency of 3% are realized. A multiband barrier-discharge excilamp based on the triple mixture exhibits a potentially long lifetime.

Dynamic pressure jump in barrier-discharge excilamps

Data for the pressure jump are used to study thermodynamic processes in barrier-discharge excilamps under the conditions of a diffuse (uniform) discharge and microdischarges. It is shown that a linear relationship between the pressure jump and excilamp radiation intensity can help to control the radiation power.

Optical characteristics of plasma of I*2, Cl*2, Br*2 halogen dimer barrier-discharge excilamps

Barrier-discharge excilamps operating in homonuclear chlorine, bromine, and iodine and their mixtures with inert gases have been studied. The spectral and energy characteristics of the barrier-discharge plasma have been obtained. The conditions have been determined at which the band D′ → A′ predominates in the spectra of molecules I*2 (342 nm), Cl*2 (257.8 nm), and Br*2 (291 nm). The efficiencies of I2, Cl2, and Br2 excilamps were found to be 1.6, 2, and 3.8%.

KrCl barrier-discharge excilamps: Energy characteristics and applications (Review)

The results of investigations of planar and coaxial barrier-discharge KrCl excilamps (λ ∼ 222 nm) are reviewed. Brief information on the developed structures of radiators and power-supply units and the results of life tests are presented. The kinetics of the processes in the working gaseous medium, the possible methods for improving the energy parameters of KrCl excilamps, and prospects of their applications are reported.

Optical characteristics of radiation from N2* dimers in a barrier discharge

The spectral and power characteristics of radiation of the second positive system of nitrogen (C3Πu → B3Πg) in Ar-N2 and Ar-N2-Cl2 mixtures excited by barrier discharge have been studied experimentally. Addition of argon to N2 increased the radiation power by sixfold. In the triple mixture Ar-N2-Cl2 = 210/0.5/0.005, minor chlorine additions increased the intensity of the C3Πu → B3Πg transition by 26% compared to Ar-N2 mixtures. Radiation power density of 2.7 mW/cm2 has been achieved. In both binary and triple mixtures, the second positive system of nitrogen was the major contributor to radiation, while the contributions of the fourth positive system of N2* (D3Σu+ → B3Πg), the Vegard-Kaplan transition of N2* (A3Σu+ → X1Σg+), and the D′ → A′ band of Cl2* were negligibly small.

Generation of nanosecond pulses in a barrier-discharge XeBr excimer lamp

The subject of investigation is the coaxial two-barrier short-pulse excimer lamp based on XeBr* molecules (λ = 282 nm). When the working mixture (Xe: Br2 = 70: 1) is excited by a high-voltage pulsed nanosecond discharge at a pressure of 1 atm, the peak power of the generated radiation is on the order of 100 kW at an FWHM of 4.5 ns. If the gap between the barriers is small, a train of pulses with an FWHM of 20 ns and a repetition rate of 200 kHz may be obtained.

XeI Barrier Discharge Excilamp

Barrier discharges in Xe-I2 (100-0.04 Torr) mixtures are studied experimentally and theoretically. It is shown that the experimental efficiency and the intensity of radiation in the B → X band of XeI* (253 nm) may reach 5.5% and 9 mW/cm2, respectively. The simulation results show that the main energy loss channel is heating of ions. The radiation yield can be increased by shortening the applied voltage pulse duration.

Photoluminescence and optical transmission of diamond and its imitators

Photoluminescence and optical transmission spectra of several samples of natural and synthetic diamond and its imitators - fianite and corundum - are investigated. The band-A of luminescence at 440 nm, the vibronic N3 system of luminescence and absorption at 415.2 nm, the fundamental absorption edge at 225 nm, and the secondary absorption below 308 nm are the main identifying markers of natural diamonds. For synthetic diamonds, however, such identifying markers are the exciton luminescence at 235 nm, the band-A, and the fundamental absorption edge. Fianites can be identified by the structureless wide band at 500 nm and the wide transmission band in the entire visible range. Colored corundum samples with chrome impurities emit the narrow line at 693 nm and show the absorption band in the 500-600 nm spectral range. A new method for diamond express identification is developed on the basis of measurement of photoluminescence and optical transmission spectra of the samples. It is shown that a diamond tester can be designed combining a spectrometer and a KrCl-excilamp radiating at 222 nm.

Two-band emission source based on a three-barrier KrCl-XeBr excilamp

We have created and tested a coaxial excimer lamp (excilamp) with three barriers and two separate compartments representing serially connected gaps. The emission spectrum of the excilamp exhibits two narrow bands of comparable intensity peaking at 222 and 282 nm, representing the emission due to KrCl* and XeBr* molecules, respectively, at an average output radiant power of 1.2 W.