Laser-induced continuum structure

This work describes the atomic route to laser isotope separation. This is a process which uses intense pulsed lasers to photoionize one isotopic species of a chemical element, after which these ions are extracted electromagnetically. The paper describes only the isotopic enrichment of uranium for nuclear fuel cycles. It makes brief mention of the traditional cascade processes used at present, and then turns to the atomic physics of laser photoionization. The principles of the laser isotope separation process, important spectroscopic experiments and considerations which determine the design of a plant are described. This review concentrates on the laser ionization process, few details of vaporization of uranium metal or the extraction of ions are given.

Laser isotope separation

We present several perturbative approaches to the Jaynes-Cummings model of optical resonance with the counter-rotating terms included. We find that there exists a hitherto overlooked phase-dependence of the atomic inversion which is due to an interference between the rotating wave and counter-rotating contributions.

Counter-rotating Contributions in the Jaynes-Cummings Model

We investigate the effects of smooth laser pulses in both an autoionization system and in the laser-induced continuum structure scheme. We are particularly interested in the phenomenon of population trapping in these systems and discuss the effects of time-dependent pulses on this trapping. We present analytical solutions to both systems which hold for any pulse shape, provided the adiabatic approximation holds. We also pay special attention to the effects of large pulse energies on the trapped population, which we find to be detrimental and propose a possible solution to this problem by using chirped (time-dependent) frequencies.

https://iopscience.iop.org/article/10.1088/0953-4075/31/4/024/pdf

Time-dependent pulse and frequency effects in population trapping via the continuum

Vibrational Spectroscopy of Laser Cooled CaH+ Report Title Cold molecules and molecular ions are leading to a renaissance in the field of molecular spectroscopy just as lasercooled atoms resulted in a renaissance of atomic physics. Cold molecules enable the performance of spectroscopy with unprecedented precision. Spectroscopy with cold molecules is driven by many of its modern applications such as precision measurements, cold chemistry and quantum information. Molecular ions trapped in RF Paul traps and sympathetically-cooled with laser-cooled atomic ions have been shown to be a great platform to measure spectroscopic transitions lines at a precision beyond traditional methods, where high ion density is necessary but difficult to achieve with the classical preparations. In this thesis, we perform vibrational spectroscopy on the ?? = 10??=0 and ?? = 9 ? ? = 0 overtone of a trapped and sympathetically-cooled 40CaH+ molecular ion using a resonanceenhanced two-photon dissociation scheme. Our experiments are motivated by theoretical work that proposes comparing the vibrational overtones of 40CaH+ with electronic transitions in atoms to detect possible time variation of in the mass ratio of the proton-to-electron. Due to a lack of experimental data, we start the search using a broadband femtosecond Ti:Sapph laser and the guidance of theoretical calculations. Our initial spectroscopy opens the path for more precise measurements to detect the variation of proton-to-electron mass ratio and to search for astrophysical presence of 40CaH+. Our method fits a wide range of molecular ions that can be co-trapped and efficiently cooled by atomic ions and is the first step to higher precision measurements. This enabled us to measure high-order vibrational overtones of a molecule using only less than 300 molecules for the entire spectrum. High precision measurements on 40CaH+ are enhanced by cooling down the motional temperature ion down to the motional ground state. Future high precision measurements will be conducted on narrow transitions using techniques that transforms the internal state changes into changes in temperature of the ions of 40CaH+. VIBRATIONAL SPECTROSCOPY OF SYMPATHETICALLY LASER-COOLED CaH A Thesis Presented to The Academic Faculty

/pdf/vibrational-spectroscopy-of-sympathetically-laser-cooled-cah-37xlzlzip6.pdf

Vibrational spectroscopy of sympathetically laser-cooled CaH+

A time-development operator technique is used to describe the intense-field excitation of three-level atomic systems by laser pulses of arbitrary shape. The pulses are divided into small elements f...

P. T. Greenland

Papers

Pulse-shape Effects in Intense-field Laser Excitation of Atoms