E. A. Ryabov

Multiple photon excitation of polyatomic molecules from the many rotational states by an intense pulse of IR radiation

Abstract The investigation of the role of pulse duration in the absorption of CO 2 laser pulses by polyatomic molecules has shown that the rotational relaxation does not contribute significantly to the absorption of intense IR radiation. This proves the existence of purely radiative depletion of all rotational states in monochromatic fields of moderate intensity.

Isotopic selectivity of IR laser photodissociation of CF3I molecules

The selectivity dependence of multiphoton dissociation of CF3I on the conditions of excitation (pulse duration, concentration of the isotope under excitation and gas pressure) has been studied. It has been shown that the main mechanism of selectivity loss isV-V exchange during a laser pulse. The elaborated model is in good agreement with the experiment.

Effect of rotational relaxation on isotopic selectivity of IR multiphoton dissociation

It is shown in experiments on CF3Br that rotational relaxation may either increase or decrease the value of multiphoton dissociation selectivity. The mechanism of the influence of rotational relaxation on selective dissociation is analyzed.

Production of carbon isotopes by laser separation

Since the advent of lasers, these unique sources of highly intense and monochromatic radiation have been proposed as excellent tools to induce or catalyze chemical reactions. Due to the great interest to the problem of isotope production, investigation and application, the laser method of isotope separation has received the most attention worldwide and may be the first major commercial application of lasers to chemistry. Laser methods of isotope separation are based on high selectivity and power of laser sources of radiation. One of the most prominent method is based on the effect is isotope-selective multiphoton dissociation of molecules by IR-radiation (MLIS-method). This phenomena was discovered in Russia in 1974 and developed from scientific investigations to industrial scale production of 13C isotopes in collaboration between the Kurchatov Institute of Atomic Energy, TRINITI and Institute of Spectroscopy of RAS. Demonstration facilities for sulfur and carbon isotope separation with average productivity up to 2 g/h have been created as a result of collaboration and these systems are aimed at optimization of MLIS process and evaluation of its cost efficiency. Experiments show that laser produced isotopes are far cheaper as compared to any conventional technique. Results of basic scientific research, existing technological cooperation allow to start building a laser isotope separation plant. Light element isotopes produced there can answer a wide variety of demands in many technologies. These isotopes can be readily used in medicine, agriculture, environmental monitoring, etc.

Carbon isotopes laser separation by multiple-photon dissociation

The isotopic selectivity of multiple-photon dissociation (MPD) was first demonstrated on 10BCl3 and 11BCl3 molecules by Ambartsumiam et al. in 1974. This paper discusses experiments with MPD as an isotope enrichment method.

The application of a high pulse repetition rate CO2 laser with high average power for isotope separation by molecular dissociation in a strong IR field

Considering a SF6 molecule we demonstrate feasibility of using high pulse repetition rate CO2 laser for isotope separation by selective molecular dissociation in a strong IR field. Dependences of dissociation efficiency as well as separation selectivity on pulse repetition rate up to 150 Hz are investigated. The inherent thermal effects are discussed.

Experimental selection of molecules for isotope separation by multiple-photon dissociation in an intense IR field

Consideration is given to selectivity estimation methods during polyatomic molecules dissociation by multiple photon absorption. Taking the CH3NO2 molecule as an example, the possibilities of selectivity estimations made on the electron-excited dissociation products (luminescence) are shown, as well as on the measurements of the energy absorbed in a strong IR field being transformed into heat. Some advantages of the last method of the selectivity estimation are discussed. The experiments on nitrogen-isotopes separation in the mixture of CH314NO2 and CH315NO2 molecules are carried out when exciting thev7 vibration with the isotope shift of about 7 cm−1 and thev13 vibration with no isotope shift in the linear absorption spectrum. The contribution of secondary chemical reactions to the separation process is discussed.

Technological complex for average-mass isotope separation by powerful CO2 laser

There is a high worldwide interest in middle mass isotopes, particularly in carbon and oxygen isotopes. Over the few last years some industrial installations have been built for producing highly concentrated 13C isotope using the method of the low-temperature rectification of CO. However the cost of isotope manufacturing by this method is rather high. One of the ways to increase the output of middle-mass isotopes and to cut its costs is using laser technologies. This report is devoted to the development of the novel laser based technology for 13C isotope production.

Laser Infrared Multiphoton Noncoherent Control of Intermolecular (Isotope) Selectivity for Polyatomic Molecules on a Practical Scale

This paper discusses methods for noncoherent laser control of molecules, based on intermolecular selectivity of their excitation and dissociation by laser radiation, describes the technology developed for laser separationof carbon isotopes, based on the IR multiphoton dissociation of Freon-22 molecules by CO 2 laser radiation, and presents the results of developing a two-stage laser process for the production of highly enriched (> 99%) carbon-13.

Production of Gram Quantities of Highly Enriched Carbon-12 by Selective Infrared Dissociation

Selective infrared dissociation of molecules is one of the perspective industrial methods of isotope separation. This is due to the availability of rater powerful (≅1 kW)and economicalir sources high repetition rate (HRR) CO2-lasers and also to the extensive experimental data on the selective it dissociation of moleculesl.