Highly selective and efficient multiphoton dissociation of polyatomic molecules in multiple-frequency IR-laser fields

Evseev, A. V.; Letokhov, V. S.; Puretzky, Alexander A.

doi:10.1007/bf00694695

Cited by 43 publications

(13 citation statements)

References 36 publications

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“…This improvement is less than the factor of 10 reported for two-frequency irradiation (P8 + P34) in [6]. We suppose that the difference is connected with temporal characteristics of the laser pulses.…”

Section: Multi-wavelength Irradiationcontrasting

confidence: 54%

“…Although the change of buffer gas and the improved beam quality probably contributed to this improvement, the role of the two-wavelength irradiation is more important: The increased selectivity observed with 9P16 + 9P28 allows to work at energy densities as high as • .... = i0 J / c m 2. In fact the authors of [6] chose a pressure of 7 mbar of Ct-ICIF2 + 25 mbar of Xe, which is much less than the 50-100mbar of CHC1F2 used in many experiments with TEA lasers. Irradiation by up to 5 wavelengths gave no better results.…”

Section: Resultsmentioning

confidence: 99%

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Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser

Fuß

Göthel

Ivanenko

et al. 1992

Z Phys D - Atoms, Molecules and Clusters

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13C isotope separation by multiphoton dissociation of CHC1F2 was studied by a continous-discharge CO2 laser Q-switched at 8 kHz. This laser can easily emit two or more wavelengths with good spatial and temporal overlap. The best irradiation results were obtained by the line pair 9P16 + 9P28. After optimizing also the pressures of CHC1F 2 and of buffer gases (He and Ar), the energy density and the gas speed, the process is now much less nonlinear than in previous experiments with a single wavelength. Differences to the TEA laser induced process were observed, and generally the pressure influence on yield and selectivity showed a variety of phenomena. They were interpreted in terms of collisional changes of spectra during the laser pulse.

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Section: Multi-wavelength Irradiationcontrasting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser

Fuß

Göthel

Ivanenko

et al. 1992

Z Phys D - Atoms, Molecules and Clusters

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“…At 100 mbar we observe an increase in the per volume dissociation yield by a factor of 1.5 compared to the 2 2 band, which reflects the ratio of the 2 1 to 2 2 absorption cross sections. While there is a decrease in the pre-excitation 4 Isotopic selectivity (a), relative IRMPD yield (b) and the absolute yield (c) as a function of CF 3 H pressure in the case of pre-excitation to the 2 2 level (filled markers) and the 3 1 level (open markers). The absolute yield is given in units of 13 C atoms per cm 3 and per J/cm 2 pre-excitation fluence.…”

Section: R E S U L T S 31mentioning

confidence: 99%

“…The photon energy expenditure of 97 eV per separated atom is much lower than that of the current commercial laser technology, making this process economically feasible. While the use of infrared lasers for molecularbased separation of stable isotopes has led to many interesting findings and promising demonstrations [1][2][3][4][5][6][7], few laser isotope separation schemes have reached the stage of commercial application [8]. In the case of schemes based on infrared multiphoton excitation, the limitation is their low isotopic selectivity.…”

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confidence: 99%

Efficient, highly selective laser isotope separation of carbon-13

2006

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We recently demonstrated an original approach to highly selective laser isotope separation of carbon-13 that employs vibrational overtone pre-excitation of CF 3 H together with infrared multiphoton dissociation [O.V. Boyarkin, M. Kowalczyk, T.R. Rizzo, J. Chem. Phys. 118, 93 (2003)]. The practical implementation of this approach was complicated by the long absorption path length needed for the overtone excitation laser beam. In the present work, we employ a low overtone level for the pre-excitation that shortens this pathway, facilitating engineering of the process. We propose an optimal configuration of the isotope separation scheme and consider a realistic example of a separation unit for isotopic enrichment of carbon-13 to 94%-98%. The photon energy expenditure of 97 eV per separated atom is much lower than that of the current commercial laser technology, making this process economically feasible. While the use of infrared lasers for molecularbased separation of stable isotopes has led to many interesting findings and promising demonstrations [1][2][3][4][5][6][7], few laser isotope separation schemes have reached the stage of commercial application [8]. In the case of schemes based on infrared multiphoton excitation, the limitation is their low isotopic selectivity. Physical methods of isotope separation, such as low temperature distillation of CO in the case of carbon, do not alter the working molecule, and this facilitates the implementation of a multi-cycle separation process [9]. Although the selectivity of each cycle is low, the repetition of many separation cycles makes it possible to achieve the high levels of selectivity demanded by the market. Because molecular laser isotope separation techniques that are based on infrared multiphoton dissociation chemically convert the parent molecule into a new species, repetitive cycles can be complicated and costly. Development of a single-stage, energy-efficient, laser separation technique that could produce the high levels carbon-13 enrichment required by the market (above 95% or above 99%) would fill an important niche.u Fax: +41-21-693-5170, E-mail: Oleg.Boiarkin@epfl.chOver the last several years we have developed a highly selective separation scheme for carbon-13 that combines isotopically selective vibrational overtone pre-excitation (OP) of the CH-stretch vibration in 13 CF 3 H followed by selective IRMPD of the pre-excited molecules (Fig. 1) [10][11][12]. The CF 2 fragments combine via 3-body collisions to form C 2 F 4 , which can be separated from the starting material. We have demonstrated selectivities up to 9000 (99% enrichment in carbon-13 starting from CF 3 H in natural abundance) that can be enhanced at high sample pressure by V-V collisional relaxation [11]. Since our original discovery of this unexpected effect [11], we have taken several steps that significantly increase the yield of the process, bringing it closer to commercial relevance. In particular, overlapping the preexcitation laser pulse with a short (50 ns) dissociation pulse ...

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“…1,2) Since early observations on isotope effects by Letokhov et al, many efforts have been made for the application of IRMPD to practical isotope separation. [3][4][5][6][7][8][9][10][11][12][13][14][15] Most studies are concerned with 13 C separation by IRMPD of fluorohydrocarbons. Baranov has reported the production of enriched 12 C (atomic fraction, 99.99%; production rate, 1 g/h) by IRMPD of natural CF 3 I using a high repetition CO 2 laser.…”

Section: Introductionmentioning

confidence: 99%

High Enrichment of²⁸Si by Infrared Multiple Photon Decomposition of Si₂F₆

Yokoyama

Ohba

Shibata

et al. 2002

Journal of Nuclear Science and Technology

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High enrichment of 28 Si has been carried out using the laser isotope separation technique based on the isotopically selective infrared multiple photon decomposition of Si 2 F 6 . When about 2 Torr of Si 2 F 6 was irradiated at a fluence of 1.0 J/cm 2 per pulse with the 10P(8) line of a TEA CO 2 laser at 954.55 cm −1 , the compound decomposed very efficiently with high isotope selectivity. The products SiF 4 and white solids were enriched with 29 Si and 30 Si, while the residual Si 2 F 6 was enriched with 28 Si. The atomic fraction of 28 Si in residual Si 2 F 6 increased with increasing decomposition of Si 2 F 6 ; 99.9% of 28 Si was obtained at a consumption of 50% of initial Si 2 F 6 . The large-scale flow experiment yielded 99.7% 28 Si at a production rate of 2.5 g/h, where a mixture of 3.3 Torr Si 2 F 6 and 6.6 Torr argon was irradiated with 10P(8) laser pulses at a repetition rate of 5 Hz. Merits and demerits of the present laser separation are discussed in comparison to those of conventional separation methods. Laser enrichment of 28 Si seems promising for economical production of large quantity of pure 28 Si. Various applications of silicon isotopes are briefly reviewed.

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Highly selective and efficient multiphoton dissociation of polyatomic molecules in multiple-frequency IR-laser fields

Cited by 43 publications

References 36 publications

Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser

Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser

Efficient, highly selective laser isotope separation of carbon-13

High Enrichment of²⁸Si by Infrared Multiple Photon Decomposition of Si₂F₆

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Highly selective and efficient multiphoton dissociation of polyatomic molecules in multiple-frequency IR-laser fields

Cited by 43 publications

References 36 publications

Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser

Isotope selective dissociation of CHClF2 by a one- and two-wavelengthQ-switched CO2 laser

Efficient, highly selective laser isotope separation of carbon-13

High Enrichment of28Si by Infrared Multiple Photon Decomposition of Si2F6

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High Enrichment of²⁸Si by Infrared Multiple Photon Decomposition of Si₂F₆