RU2531178C2 - Method for laser separation of hydrogen isotopes - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to molecular physics, specifically to separation of hydrogen isotopes, and can be used to separate the deuterium isotope D. The method for laser separation of hydrogen isotopes includes irradiating starting hydrogen chloride HCl gas with resonance infrared radiation with wavelength of 4.662 mcm, subsequent irradiation with laser radiation in the optical or infrared range with intensity greater than 10¹³ W/cm² and extracting the formed positive ions, wherein the time between irradiation with resonance infrared radiation and laser radiation must not exceed the decay time of the oscillatory state of deuterium chloride DCl.

EFFECT: invention improves the efficiency of separating hydrogen isotopes.

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Description

The invention relates to molecular physics, and in particular to the field of separation of hydrogen isotopes, and can be used to isolate the isotope deuterium D.

Chemical methods for the separation of hydrogen isotopes are known [RF patent 2201283, IPC B01D 59/04 of 11/21/2001], in which two feed streams from protium, tritium, and deuterium are processed in cryogenic distillation columns and homomolecular isotopic exchange units. The disadvantage of this method is the high cost of the separation process.

Known methods for the separation of hydrogen isotopes using infrared laser technology in combination with chemical processes. In particular, in patent CA1103614 [IPC B01D59 / 34, С01В 4/00, СВВ 5/02 from 1977-12-01] acetic or formic acid containing deuterated and hydrogenated acids compounds are irradiated with a wavelength in the infrared spectrum from 9 , 2 to 10.8 μm, to obtain deuterium hydroxide and deuterium hydride, respectively. In the patent CA1085341 [IPC B01D 59/34, C01B 4/00, C01B 5/02, H01S 3/00 from 1976-07-19] deuterium from natural sources is isolated using tuned infrared lasers, and molecules containing deuterium are separated from source material by absorption, distillation or other chemical methods.

Laser isotope separation methods are effective methods for producing chemical elements of a certain isotopic composition [Letokhov BC, Moore SB Quantum Electronics, vol. 3, issue 3, 4, 1976], which is associated with the possibility of significant isotopic enrichment in one cycle. Laser isotope separation methods are based on the selective excitation by laser radiation of electronic or vibrational levels of atoms or molecules of a certain isotopic composition. The method of selective stimulation of one molecular component in a mixture [WO 9712373, B01D 53/00, B01D 59/34, G01N 21/63 from 1997-04-03] involves the transition of both components to the first excited state at the first laser pulse and a selective transition of one component to the second excited state with a second laser pulse of 10 ^-15 s duration. The time between two pulses should be equal to the integer number of half-periods of the resonance period of the selected component.

The known method [patent GB1473330, IPC B01D 59/34, B01J 19/12, G02B 27/00, H01S 3/00, H01S 3/094, H01S 3/22 from 10.23.1973] laser isotope separation, taken as a prototype based on isotopically selective excitation of gas phase molecules during infrared absorption of photons, which includes the following stages: irradiation of molecules with PC radiation using an IR laser at an intensity of at least 10 ⁴ W / cm ² from 10 ^-10 to 5 × 10 ⁻⁵ s, with molecules containing the desired isotope or isotopes predominantly excited by resonant radiation and absorb more than one guy of PC radiation; the conversion of excited molecules during laser irradiation of the optical or UV range for photodissociation, in which the excited molecules can be separated from unexcited.

Selective vibrational excitation is considered the most difficult method [Letokhov B.C., Moore SB, cit. Cit., P. 253]. This is due to the fact that, despite the simplicity of selective vibrational excitation, it is difficult to further isolate vibrationally excited molecules.

The objective of the invention is to eliminate the disadvantages inherent in the prototype.

The technical result consists in increasing the efficiency of hydrogen isotope separation by laser separation.

The technical result is achieved by the fact that in the method of laser separation of hydrogen isotopes, which includes irradiating the source gas with resonant infrared radiation, subsequent exposure to laser radiation and extraction of the generated positive ions according to the invention, hydrogen chloride (Hcl) is used as the source gas, the wavelength of resonant infrared radiation is 4.662 μm laser radiation optical or infrared range, and the intensity is greater than 10 ¹³ W / cm ² and the time between exposures resonances Nogo infrared laser radiation and should not exceed the decay time of the vibrational state of DC1.

It is proposed to use the effect of anti-Stokes amplification of tunnel ionization of molecules. This effect, proposed and described in [Komev A.S., Zon B.A. Phys. Rev. A 86, 043401 (2012)], consists in a significant increase in the probability of the tunneling effect in the laser field for vibrationally excited molecules. With the tunneling effect in the laser field, an inelastic process is possible when part of the energy is transferred to the tunneling electron from other degrees of freedom in the atoms [Komev A.S. et al. Phys. Rev. A 68, 065403 (2003); 69, 065401 (2004); 79, 063405 (2009); 84, 053424 (2011); 85, 035402 (2012)] or molecules [Komev A.S., Zon B.A., Phys. Rev. A 86, 043401 (2012)]. For molecules, such other degrees of freedom may be the vibrational degrees of freedom of the nuclei of the atoms that make up the molecule. The preliminary excitation of nuclear vibrations allows the formation of ions with the predominant content of certain isotopes as a result of the tunneling effect, since neutral molecules of different isotopic composition have different frequencies of vibrational transitions.

Figure 1 shows the dependence of the probability of formation of DCF ⁺ ions from an excited vibrational state (v _i = 1) to the probability of formation of Hcl ⁺ ions from the ground vibrational state (V _i = 0) on the laser radiation intensity I [W / cm ² ].

Hydrogen chloride gas containing deuterium (deuterium in natural hydrogen is approximately 1.5%) is irradiated with a wavelength of 4.662 μm to populate the first vibrational state of the DC1 molecule. After that, the gas volume subjected to irradiation with the above wavelength is affected by laser radiation of the optical or infrared range, and the radiation intensity I must be high enough so that the ionization passes due to the tunneling effect, i.e. satisfy inequality

, $$I>2{\alpha }_e^{-2}{\left(\frac{2\pi \alpha }{\lambda }\right)}^2\frac{E_0}{E_{\alpha }}{I}_{\alpha }$$

,

where E ₀ is the ionization potential of the molecule; λ is the wavelength of ionizing radiation; α = 0.529 Ǻ = 0.529 × 10 ^-10 m - atomic unit of length (Bohr radius); Eα = 27.2 eV = 4.36 × 10 ^-18 J - atomic unit of energy; I _α = 3.51 × 10 ¹⁶ W cm ^-2 = 3.51 × 10 ²⁰ Wm ^-2 - atomic unit of intensity; α _e = 7.23 × 10 ^-3 is the fine structure constant.

For a hydrogen chloride molecule Hcl and its isotopic modification DC1, this intensity should exceed 4 × 10 ¹³ W / cm ² at a wavelength of ionizing radiation of 1.3 μm or 1.6 × 10 ¹³ W / cm ² at a wavelength of ionizing radiation of 2.0 microns. The time interval between irradiation with resonant infrared radiation and high-power laser radiation should not exceed the lifetime of the vibrational state, which depends on the pressure and temperature of the gas. Due to the tunneling effect, vibrationally excited molecules, i.e., DC1 molecules, are predominantly ionized. Then, by extraction of positive ions, hydrogen chloride is obtained with an increased, compared to natural, deuterium content.

From the dependence in FIG. 1, it can be seen that under optimal conditions, with a laser radiation intensity of ~ 10 ¹³ W / cm ² , the probability of formation of DCF ions exceeds the probability of formation of HC1 ⁺ ions by more than 20%.

Claims (1)

The method of laser separation of hydrogen isotopes, including irradiating the source gas with resonant infrared radiation, subsequent exposure to laser radiation and extraction of the generated positive ions, characterized in that the source gas is hydrogen chloride (HCl), the wavelength of the resonant infrared radiation is 4.662 μm, the laser radiation range optical or infrared, and the intensity is greater than 10 ¹³ W / cm ² and the time between the effects of resonance and infrared laser radiation not ave to exceed the decay time of the vibrational state DCl.

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