While Eric Adelberger (UWash) was on sabbatical leave at CERN during the academic year 1993-94, a discussion developed between us of the published claims by theorist Emilio Santos (see references in our paper below) that quantum mechanics may be interpreted within the framework of so-called local hidden-variables models without conflict with any known experiment. We found to be correct his criticism of the use of Bell's inequalities to draw contrary conclusions from experiments by Aspect and others, but were not convinced that the experimental deficiencies were fundamental, as Santos further conjectured. In a subsequent paper published in PRL we presented a realistic (although extravagant) experiment which defeats Santos' conjecture that Bell's inequalities are in principle inaccessible to experimental tests.
In informal discussions with UConn physics major Glen Maclachlan about the Stern-Gerlach experiment, which provided experimental confirmation of theoretical ideas about space quantisation and intrinsic spin, we looked into the comparison between the behaviour expected for classical and quantum spinors. In the process we discovered some surprising subtleties in the problem which are ignored in most textbook treatments of the subject. For more information about this work, see Glen's senior research project.
UConn graduate student Chunlei Guo (graduated 1998) studied for his thesis project the ionization rates of atoms and molecules in the intense field of a short-pulse high-power laser, under the guidance of UConn professor George Gibson. His results showed a significant excess in the double-ionization rate over what would be expected if the two electrons were emitted in a sequence of two single-ionization steps. This effect, called non-sequential double ionization (NSDI) had been observed by others before. What Chunlei discovered was that the NDSI rates for diatomic nitrogen and oxygen were different, an effect which he hypothesized to be due to the different symmetries of the valence electrons in the two molecules. Following discussions of these ideas with Chunlei and George, we embarked on a project to numerically simulate the two-electron system in the presence of the ionizing field. With a little effort, the code developed with Glen Maclachlan (see above) was revamped to describe the two-electron atom with a time-varying background potential. Chunlei then used this code to simulate both single and double-ionization. With it he was able to reproduce the NDSI effect, and observed a significant dependence in the NDSI rate on the symmetry of the initial two-electron state, in agreement with his experimental observations.
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