Photochemical isotope separation

Tobin J. Marks (NAS) is the Charles E. and Emma H. Morrison Professor and Vladimir N. Iptieff Professor of Chemistry at Northwestern University. Through landmark synthetic, mechanistic, and thermodynamic investigations, he and his students opened a new portion of the Periodic Table to organometallic chemistry. He has also made major advances in solid state, polymer, bioinorganic, and boron hydride chemistry and in photochemical isotope separation. He received his B.S. from the University of Maryland and his Ph.D. from Massachusetts Institute of Technology. 

Perhaps the most intriguing photochemical isotope separation that has been reported is that which occurs when SF is subjected to high intensity pulses from a... 

The essential requirements for any photochemical isotope separation scheme follow ... 

Laser-induced plasma spectroscopy (LIPS), archaeological materials, 5 743 Laser isotope separation, 25 416 417 Laser light, 14 655-656 Laser light sources, in photochemical technology, 19 107-108... 

Selective excitation of wavepackets with ultrashort broadband laser pulses is of fundamental importance for a variety of processes, such as the coherent control of photochemical reactions [36-39] or isotope separation [40--42]. It can also be used to actively control the molecular dynamics in a dissipative environment if the excitation process is much faster than relaxation. For practical applications it is desirable to establish an efficient method that allows one to increase the target product yield by using short laser pulses of moderate intensity before relaxation occurs [38]. 

The first three requirements relate to the inherent chemical properties of the mixture to be separated. The requirements for the light source depend on the properties of the mixture, but its availability is a technological variable. Lasers, with their narrow wavelength ranges and high intensities, have generated new interest in photochemical separations. Infrared lasers have also made possible the completely new field of infrared-induced chemistry, in which some significant isotope separations have been reported. 

Our examination of the photochemical literature of uranium clearly shows that extensive attention has been given to UFg, while other compounds, until recently, have been almost ignored. The attention given to UFg, of course, relates back to the great interest in achieving a low cost laser induced isotope separation process for uranium isotopes. The economics of isotope separation, which have been briefly discussed by Letokhov and Moore (61), have consequently dictated the direction of much of the applied photochemical research on uranium compounds. Nonetheless, from the existing spectroscopic and photochemical data outlined here it would be expected that coordination and... 

Urey, H. C. "Investigations of the Photochemical Method for Uranium Isotope Separation," Project SAM, Columbia University, July 1943 (A-750). 

Although the formidable difficulties associated with isotope separation schemes based on photochemical vibrational excitation plus chemical reaction continue to attract considerable attention, some earlier hopes appear to have been dashed. An experiment performed in 1970 by Mayer et al. has been much quoted. They reported irradiating mixtures of CHjOH and CD3OD in the presence of Bts with lines from an HF laser that are absorbed only by CH3OH. Product analysis indicated the selective depletion of the CH3OH. This observation was interpreted in terms of a selective reaction between vibrationally excited CH3OM and Bra, nnd it appeared to point the way to an economic method for the production of heavy water. However, the results of a careful re-examination of this system have just... 

In this paper a number of isotope separating processes will be examined, particularly those utilized on a large Industrial scale, and the bases for the above conclusions will be presented. Finally, the fundamental principles of a photochemical method of Isotope separation based upon excitation by laser light, which has excited a great deal of current Interest, will be outlined. 

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