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

: Wakai A, Tsuchida K, Fukumura T, Iida H, Suzuki K

Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE

: 2012

: Journal of Molecular Spectroscopy

: JOURNAL OF MOLECULAR SPECTROSCOPY

: J MOL SPECTROSC

: 274

: 14

: 21

: 8

: 0022-2852

DOI: https://doi.org/10.1016/j.jms.2012.03.004

We observed that the two-photon excitation of a v(3) 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 x 10(-48) (cm(4) 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. (c) 2012 Elsevier Inc. All rights reserved.