Theoretical investigation of the kinetics and of the energy characteristics of electron-beam-controlled discharge lasers

Mathematical simulation of the physical processes in an active medium is used to carry out detailed theoretical investigations of the kinetics and of the lasing characteristics of electron-beam-controlled (EB) discharge lasers operating on vibrational-rotational transitions of the molecules C0₂, CO, H₂, and HD. The power, energy, efficiency, and lasing spectrum are obtained as functions of the composition of the active medium and of the pumping conditions (the value of E/N, the power and duration, the spatial homogeneity). The influence of the isotopic composition of the carbon monoxide on the lasing characteristics of a CO laser is studied. The restrictions connected with the breakdown of the active medium by its own radiation are investigated for CO₂, H₂, and HD molecules.This article is a report of the results of theoretical investigations of electron-beam-controlled discharge lasers performed at the Quantum Radiophyiscs Laboratory of the Lebedev Institute in 1973–1977.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva Akademii Nauk SSSR, Vol. 116, pp. 7–53, 1980.     

Pulsed-periodic laser on RM helium and strontium transitions

Conditions of generation of a running excitation wave in the active medium of gas lasers and efficiency of the running wave application for pumping of the active medium are considered by the example of a strontium vapor laser. It is demonstrated that the running excitation wave is generated directly in the active laser medium and is supported by the energy stored in the capacitive component of the impedance of a gas-discharge tube. Generation on the self-limited (2¹P₁-2¹S₀) transition of the helium atom at λ = 2058 nm and simultaneous generation on RM transitions of the strontium ion and strontium and helium atoms and on a number of neon atom transitions is first excited. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 6–9, January, 2008.     

Coadsorption de l'oxygène et du monoxyde de carbone sur des surfaces de rhénium

Temperature programmed desorption ($\text{2.65}\text{K}\text{sec}$) has been used to study carbon monoxide and mixed layers of carbon monoxide and oxygen on rhenium ribbons, strongly oriented parallel to the (0001) plane. Four binding states, populated in decreasing energy have been detected. Interpretation of the results on β states agrees qualitatively with King's model postulating dissociation of carbon monoxide molecules and a repulsive interaction energy between carbon and oxygen atoms. However, in the coadsorbed layers studies, it is shown that all the oxygen atoms do not play a part in the recombination process, during desorption, and that when oxygen is adsorbed after carbon monoxide, a displacement reaction occurs, due to apparent transfer from β states towards molecular α states. Optimization of the results on pure carbon monoxide layers leads to an interactional energy ω, equal to 3 $\text{kcal}\text{mole}$, and is only possible if is assumed that β states are formed on alternatively filled and empty rows.     

Millimeter-wave spectroscopy of weakly bound molecular complexes: Isotopologues of He-CO

Van der Waals complexes consisting of helium atoms and carbon monoxide molecules, He-¹²C¹⁶O, He-¹³C¹⁶O, He-¹²C¹⁸O, and He-¹³C¹⁸O are studied in the frequency range 110–140 GHz on an intracavity orotron-based spectrometer. Ten new lines, which correspond to rotational transitions and transitions to the bending vibration of the complex, are detected and identified as lines belonging to the R and P branches. The positions of the energy levels of isotopologue of the He-CO complex are refined by joint analysis of both the transition frequencies measured in this study and previously published microwave and infrared data. Isotopic dependences of the positions of the He-CO energy levels are obtained. These results can serve as the starting point for studying small helium clusters with embedded CO molecules.     

A description of the laser-induced annealing and diffusion behaviour of implanted silicon crystals

Abstract

It is shown that as a result of the Greenwood-Foreman-Rimmer loop punching mechanism applied for helium bubble growth in nickel implanted with 5 keV He⁺ ions at 273 K, a considerable amount of helium remains outside the bubbles which are visible in a transmission electron microscope (TEM). It is also shown that even when it is assumed that there is an energy barrier with an upper limit equal to the formation energy of a self-interstitial atom, not all implanted helium can be accumulated in the bubbles below the critical dose for blistering.

The experimental observation of bubble growth in a helium pre-implanted nickel specimen during 1 MeV e^? irradiation may demonstrate that indeed a significant amount of helium remains between the bubbles visible in TEM.     

Laser-induced fluorescence measurements of a 3 Π metastable carbon monoxide in a high enthalpy flow

Excitation of carbon monoxide molecules has been carried out in a cold cell and in a low-pressure plasma jet using an ArF narrow-band excimer laser. The different excitation models are discussed and the relevance of atomic carbon absorption into the laser cavities is pointed out. Excitation spectra of Cameron bands have been obtained in a room-temperature cell and compared with calculated spectra. A value of the constant σ related to the interaction strength between a ³ Π( v = 2) state and its neighbouring singlet states is derived: 0≤σ≤0.05. The fluorescence spectrum following broad band excitation of CO has been observed both in UV and visible. Similar experiments carried out in a high enthalpy flow have allowed to point out the presence of a ³ Π metastable carbon monoxide. A method for relative measurements of this species concentration is proposed. Received 9 April 2001 and Received in final form 13 June 2001     

Pulsed electroionization carbon monoxide laser amplifiers

The results from the experimental studies of the parameters of the pulsed electroionization (EI) carbon monoxide laser amplifiers (LA) are presented. It is shown that the highest (~100J/1. Amagat) energy yield from the active medium of the CO EI LA is attained under spectral-temporal matching of the external signal and the amplifying medium. We have found optimal conditions for the amplification of the pulses which are not matched with the amplification medium either by the spectrum (a series of spectral components or by the time (a series of microsecond pulses). Specific energy yield of ~80J/1. Amagat from the active medium of CO EI LA has been reached for spectral components amplification, and ~25J/1. Amagat for a series of microsecond pulses.     

Nonstatistical temperature fluctuations and displacement of equilibrium

It is shown that an anomalously large displacement of equilibrium occurs in systems with rapidly oscillating temperature. The thermodynamic parameters of such a system differ substantially from the values corresponding to constant temperature. The dynamics of the distributions of hydrogen ions and impurity helium and carbon ions over ionization states in a hydrogen plasma and the dynamics of the intensity distribution of the line radiation of impurity carbon in a hydrogen plasma with oscillating temperature are calculated as an example. In systems with fluctuating temperature, the effect in question could be important in virtually all problems based on levelwise kinetics, for example, the energy balance and spectral diagnostics of turbulent plasma, the criterion of thermal stability, the dynamics of turbulent plasma and gas jets, the conditions for amplifier and oscillator operation in the active media of electric-discharge gas lasers, and so on. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 308–312 (10 March 1998)     

Study of oxygen and carbon monoxide adsorption on molybdenum (110) by metastable helium de-excitation spectroscopy

The adsorption of oxygen and carbon monoxide on the (110) face of molybdenum is studied at room temperature by metastable helium atom de-excitation spectroscopy (MDS). On the basis of the interaction mechanism described by H.D. Hagstrum, and which was shown to be valid for the He¹?Mo couple in a previous article and again here, the secondary electron energy spectra are interpretated as relating to the self-convolution product of the electron state density of occupied valence band levels of the solid. The results obtained after deconvolution show the variations in this density of states during oxygen and carbon monoxide adsorption, and they are compared with photoemission spectra (UPS) obtained at the same time as the MDS spectra. They show that MDS is a technique well suited to the study of adsorption phenomena.     

Mechanodynamic diffusion of nitrogen molecules into armco-iron under its deformation in liquid nitrogen medium

Data on mechanodynamic penetration of nitrogen molecules are obtained under deformation of armco-iron samples. It is shown that molecular nitrogen diffuses into the surface layer of samples under their deformation in a liquid nitrogen medium, and the nitrogen concentration compares well with the helium concentration in samples deformed in a liquid helium medium and in some cases exceeds the latter.     

Energy Exchanged Process of Superradiant Optically Pumped Far-Infrared Laser with Buffer Gas

By means of solving the density matrix equations, base on the mechanism model of buffer gas, the output intensity of FIR and the FIR signal gain coefficient Gs and IR pumping signal absorption coefficient Gp were calculated, energy exchanged process of superradiant OPFIRL with buffer gas was analyzed. It was found that after adding buffer gas into the laser medium, the FIR output could be increased, and the active region of a FIR laser was lengthened.     

Friction and energy dissipation mechanisms in adsorbed molecules and molecularly thin films

This review provides an overview of recent advances that have been achieved in understanding the basic physics of friction and energy dissipation in molecularly thin adsorbed films and the associated impact on friction at microscopic and macroscopic length scales. Topics covered include a historical overview of the fundamental understanding of macroscopic friction, theoretical treatments of phononic and electronic energy dissipation mechanisms in thin films, and current experimental methods capable of probing such phenomena. Measurements performed on adsorbates sliding in unconfined geometries with the quartz crystal microbalance technique receive particular attention. The final sections review the experimental literature of how measurements of sliding friction in thin films reveal energy dissipation mechanisms and how the results can be linked to film-spreading behavior, lubrication, film phase transitions, superconductivity-dependent friction, and microelectromechanical systems applications. Materials systems reported on include adsorbed films comprised of helium, neon, argon, krypton, xenon, water, oxygen, nitrogen, carbon monoxide, ethane, ethanol, trifluoroethanol, methanol, cyclohexane, ethylene, pentanol, toluene, tricresylphosphate, t-butylphenyl phosphate, benzene, and iodobenzene. Substrates reported on include silver, gold, aluminum, copper, nickel, lead, silicon, graphite, graphene, fullerenes, C60, diamond, carbon, diamond-like carbon, and YBa₂Cu₃O₇, and self-assembled monolayers consisting of tethered polymeric molecules.     

Optimization of core–valence states of molecules

ABSTRACT

Core–valence double-electron ionisation spectra of a few small molecules – carbon monoxide, ammonia, methyl fluoride and thiophene – are presented and analysed using the self-consistent field algorithm introduced by Hans Jørgen Jensen 30 years ago. It confirms the utility of this algorithm, frequently employed to obtain stable and sharp convergence of wave functions for the benefit of calculations of a great variety of molecular properties, thus also for optimisation of core–valence states and for the interpretation of the corresponding spectra.     

Mechanism for optical parametric generation in an absorbing medium

A theory that makes it possible to determine the parameter regions where amplification is observed in an absorbing medium and absorption is observed in an amplifying medium is constructed. In these regions stationary generation of a pair of symmetric modes can be established in an absorbing medium. Polychromatic pumping to other modes is the energy source. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 1, 19–24 (10 January 1996)     

Improved Five-Parameter Exponential-Type Potential Energy Model for Diatomic Molecules

The dissociation energy and equilibrium bond length as explicit parameters are used to establish an improved five-parameter exponential-type potential energy model for diatomic molecules. We demonstrate that the five-parameter exponential-type potential is identical to the Tietz potential for diatomic molecules. It is observed that the improved five-parameter exponential-type potential can well model the internuclear interaction potential energy curve for the ground electronic state of the carbon monoxide molecule by the utilization of the experimental values of three molecular constants.     

Bipolar atmospheric-pressure corona discharge in a He/H2 mixture

Results are presented from a study of the characteristics of a steady-state plasma in a He/H₂ mixture at high pressures. The plasma is formed in the outer region of a multielectrode corona discharge. It is shown that molecules of helium hydride form in such a medium, and their decomposition is accompanied by continuum emission in the 350–650 nm region. The corona discharge is distributed over the length and can be used in systems for the transverse electric circulation of the working medium of atmospheric-pressure plasma radiation sources. The reference spectra of the plasma emission and the dependence of the relative intensity of the lines and the brightness of the bands of He ₂ ^* on the value of the discharge current, pressure, and composition of the working mixture are investigated. Zh. Tekh. Fiz. 69, 33–37 (July 1999)     

基于光放大的长脉冲抽运太赫兹激光

为了获得较窄增益带宽、较大光强的太赫兹辐射,尝试了利用TEA CO₂激光器对6 W可调谐连续波CO₂种子激光实行双程光放大实验,以期望获得长脉冲、高峰值功率的抽运光.通过实验,获得了大约30倍的放大系数,放大光输出功率随种子光注入功率的增加而增加,其中10 P （20）支线表现更加突出,并且被放大的激光支线半峰全宽在14 μs左右.基于这种长脉冲抽运源,建立了一种产生脉冲太赫兹的动力学模型,给出了产生太赫兹辐射的饱和抽运光强表达式,确定了抽运光的光强范围.另外, 关键词： 激光物理 长脉冲 动力学模型 太赫兹激光     

Electron production by metastable rare gas atom impact on a molybdenum (110) surface

Electron production by impact of thermal energy metastable helium, argon, and xenon atoms on a molybdenum (110) surface was studied. The electron yield was always highest for a clean surface and decreased considerably when the surface was exposed to either oxygen or carbon monoxide. The change in electronic yield with gas coverage of the surface was most drastic for xenon and smallest for helium metastables. The similarity of the present results to earlier measurements of electron production by low energy noble gas ion impact led us to believe that metastable deexcitation proceeded via resonance ionization followed by Auger neutralization in the present cases.     

Microhardness of armco iron samples with different initial structures after rolling in a helium or nitrogen medium

We have analyzed the dependences of microhardness H on load P for the surface layers of Armco iron samples with different initial structures, i.e., annealed and after equal-channel angular pressing (ECAP). The microhardness was measured in air after rolling of the sample in helium or nitrogen medium. It has been found that these mediums produce different effects on the H(P) dependences for preliminarily annealed samples compared to those subjected to ECAP. This is due to the differences in their initial defects structures and in the types of binding forces of helium atoms and nitrogen molecules with dislocations, which determine the intensity of their penetration into the surface layer of the samples under investigation. We have obtained curves that describe the release of helium from samples rolled in different mediums and have measured the amount of helium.

     

Study of the limiting energy characteristics of a combined discharge in a gas flow

A combined method of excitation of a gaseous medium is used in an investigation of the energy characteristics of a non-self-sustaining discharge as functions of the capacitance of the capacitor bank, the number of pulses per burst, and the burst repetition rate for different time intervals between the pulses in a burst and different flow velocities of the gas. It is shown for infrared lasers that under optimal pumping conditions the average discharge power can reach 8.5 W/cm³ for a pulse power of 25 W/cm³. Zh. Tekh. Fiz. 68, 33–38 (May 1998)