Laser isotope separation of 13C by an elimination method

doi:10.1016/0009-2614(83)80366-2

Chemical Physics Letters

Volume 95, Issue 6, 18 March 1983, Pages 614-617

https://doi.org/10.1016/0009-2614(83)80366-2 Get rights and content

Abstract

An elimination method is presented for laser isotope separation. It consists of flow cycles of feed molecules, in which an isotope component of non-interest, instead of the one of interest, is photolyzed to be eliminated, and the residue is recycled for photlysis. An isotope can be enriched as much as desired even if the isotope selectivity in the photolysis is low. The separation of ¹³C is demonstrated by employing multiphoton dissociation using a TEA CO₂ laser.

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Cited by (17)

Determination of two-photon-excitation cross section for molecular isotope separation
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We observed that the two-photon excitation of a v₃ hot band (6s Rydberg $3; 3_{1}^{0}$ ) in methyl iodide is promising for isotopic laser separation, because the isotope shift of the multiphoton ionization (MPI) resonance is resolvable. To estimate the excitation cross section, which gives the enrichment factor (final isotope ratio per initial isotope ratio) of the separation method, we devised a method based on a pump–probe MPI procedure. By probing the material remaining after irradiation with the pump pulse, we estimated the cross section of the ground-state transition (6s Rydberg 3;0–0) to be 4.1 ± 1.4 × 10⁻⁴⁸ (cm⁴ s). The enrichment factor predicted from this cross section indicates that a high-performance laser system (20 mJ/pulse, 200 Hz, 10 ns duration) was capable of achieving an enrichment of over 1000-fold in view of the dissociation efficiency under low-pressure gas conditions. Thus, laser separation (elimination) appears to be a promising tool to create positron-emission tomography molecular probes.
Isotopic effect in the (2+1) REMPI spectra of 13C-substituted methyl iodide for UV selective dissociation
2011, Chemical Physics Letters
Citation Excerpt :
1) In Case 1, we set the laser wavelength at the peak wavelength of 11CH3I, which causes the 11CH3I molecules to dissociate; we can then chemically fix the resulting methyl radical fragments using scavenger molecules and use the fixed fragments for radiotracer synthesis. ( 2) In Case 2, known as the ‘elimination method’ [30], we set the laser wavelength at the peak wavelength of 12CH3I, which causes the 12CH3I molecules to dissociate; we can then chemically eliminate the resulting fragments and use the remainder of the sample, now enriched with 11CH3I molecules, for radiotracer synthesis. For Case 1, the enrichment factor (ratio of final to initial isotope concentrations) is less than the inverse of the ‘excitation ratio’ of the light.
To investigate a possible means of achieving isotopic enrichment of methyl iodide (CH₃I), we studied the 6s Rydberg states of ^13,12CH₃I by (2+1) resonance-enhanced multiphoton ionization. For $3; 3_{1}^{0}$ band (v3 hot band) excitation (at a full width at half maximum of 14 cm⁻¹), we observed a well-resolved isotope shift of +16 cm⁻¹. The band shape, which has a broad shoulder on the red side and an abrupt decrease on the blue side, indicates that this resonance is ideal for enriching the concentration of the desired lighter isotope (the isotopomer).
Isotopic enrichment of 13C by IR laser photolysis followed by fast bimolecular reaction
1996, Journal of Photochemistry and Photobiology A: Chemistry
The selective IR multiphoton decomposition of ¹²CF₃I in the presence of NO₂ as radical scavenger was used to obtain isotopic enrichment of ¹³C in a one- stage process. The ¹²CF₃ radicals produced by IR photolysis react with NO₂ through a fast bimolecular reaction to yield ¹²CF₂O together with undissociated ¹³CF₃I as the main carbon-containing products. The isotopic enrichment increases with the [NO₂]/[CF₃I] ratio. The results are compared with those obtained using O₂ as scavenger.
The laser wavelength influence on the 13C separation by the IRMPD of CF<inf>2</inf>HCl molecules
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Two-stage IRMPD process for practical 13C enrichment. CHClF<inf>2</inf>/Br<inf>2</inf> mixtures
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Highly selective 13C separation by CO<inf>2</inf>-laser-induced IRMPD of CF<inf>2</inf>Cl<inf>2</inf>/HI and CF<inf>2</inf>ClBr/HI mixtures
1987, Chemical Physics Letters
The CO₂-laser-induced IRMPD of CF₂CL₂/HI and CF₂ClBr/HI mixtures produced ¹³C-enriched CF₂HCl. In CF₂Cl₂/HI mixtures, the CF₂HCl underwent secondary IRMPD in the continuing pulse irradiation at the same wavenumber and fluence, yielding CF₂H₂ with a ¹³C content of 97%. Because of efficient decomposition at relatively low fluences, CF₂ClBr seems to be a promising starting molecule in two-step ¹³C enrichment.

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Chemical Physics Letters

Abstract

References (12)

Laser Focus

Rev. Laser Eng. (Japan)

J. Chem. Phys.

Cited by (17)

Determination of two-photon-excitation cross section for molecular isotope separation

Isotopic effect in the (2+1) REMPI spectra of <sup>13</sup>C-substituted methyl iodide for UV selective dissociation

Isotopic enrichment of <sup>13</sup>C by IR laser photolysis followed by fast bimolecular reaction

The laser wavelength influence on the <sup>13</sup>C separation by the IRMPD of CF<inf>2</inf>HCl molecules

Two-stage IRMPD process for practical <sup>13</sup>C enrichment. CHClF<inf>2</inf>/Br<inf>2</inf> mixtures

Highly selective <sup>13</sup>C separation by CO<inf>2</inf>-laser-induced IRMPD of CF<inf>2</inf>Cl<inf>2</inf>/HI and CF<inf>2</inf>ClBr/HI mixtures