Abstract
The influence of multi-line pulsed excitation of target isotopes within the method of selective laser assisted retarded condensation (SILARC) on the efficiency of boron isotopes separation is investigated. In pulsed mode simultaneous excitation of all four isotopologues 11B35Cln37Cl3−n is possible. In order to study it, a new formula for multi-line excitation rate is derived. The total number of photons absorbed by target isotopologues for proposed physical parametrization of the laser pulse is compared with continuous wave excitation case, corresponding to the minimal level of laser intensity, required to excite all four isotopologues. It is found that irradiation efficiency of the pulsed mode is 20.59 times smaller than for CW-mode one. Influence of multi-pass cavity on the efficiency of excitation has been also considered.
Highlights
Control of atomic and molecular scale systems using laser pulses arises in many problems of chemical physics.[1,2,3,4]
Target gas is seeded at very low molar fraction (μ ∼ 0.02) into argon used as a carrier gas in order to minimize nearly resonant VV excitation loss caused by collisions among BCl3 molecules
Since BCl3 photoabsorption spectrum has four lines related to different combinations of chlorine isotopes, using multi-line pulsed irradiation mode within the method of selective retarded condensation (SILARC) seems attractive, due to possibility of almost instantaneous excitation of all four isotopologues of BCl3, and CO2 laser emission spectrum has four adjacent strong emission lines in the close proximity of photoabsorption lines
Summary
Control of atomic and molecular scale systems using laser pulses arises in many problems of chemical physics.[1,2,3,4] Multi-line laser radiation, sometimes together with incoherent control by incoherent light, pressure and temperature, is used to control of chemical reactions, molecular alignment, laser assisted isotope separation, etc.[5,6,7,8,9,10,11,12,13] In this paper we exploit control by multi-line pulsed laser radiation for SILARC method[14] to recover boron isotopes by multi-line pulsed laser radiation. CO2 laser was chosen for selective excitation of target isotope containing molecules (isotopologues) due to its highest efficiency comparing to other lasers on the market. Taking this into account, appropriate gas molecule, having photoabsorption spectrum that matches its emission spectrum, should be chosen. It is natural to look for application of pulsed operation mode of CO2 laser, that can provide almost simultaneous excitation of all of them. Another important advantage of pulsed irradiation is, that energy extraction level from CO2 laser medium is higher than for single lasing mode, and, the electric energy consumption is expected less to recover the same amount of isotopes. Efficiencies of using laser energy for boron isotopes excitation in pulsed and continuous modes are compared
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