Recent advances in pulsed electron gun technology have resulted in femtosecond electron pulses becoming available for ultrafast electron diffraction experiments. For experiments investigating chemical dynamics in the gas phase, the resolution is still limited to picosecond time scales due to the velocity mismatch between laser and electron pulses. Tilted laser pulses can be used for velocity ma...

We study the cross-correlation between the spin and orbital parts of magnetic dipole transitions M1 in both isoscalar and isovector channels. In particular, we closely examine certain cases where ∑ B(M1) is very close to ∑ B(M1)σ + ∑ B(M1)l, implying a cancellation of the summed interference terms. We gain some insight into this problem by considering special cases approaching the SU(3) limit, ...

1.1 Outline The central conceptual difficulty in standard non-relativistic quantum chemistry, as for relativistic quantum mechanics, remains that in the absence of a satisfactory, physically intelligible representation of the phenomenon of spin, spin is represented in our models as a topological constraint on many-particle interactions. All of chemistry is dominated by the phenomenon of spin-pa...

We give a detailed description of recent developments in reduced scaling ab initio methods for treating electron correlation in atoms and molecules. Since configuration interaction (CI) is the simplest electron correlation method, it is introduced first and used as a context to describe the familiar local correlation and pseudospectral approximations. The article then goes on to discuss the app...

We propose to quantify the correlation inherent in a many-electron (or many-fermion) wave function psi by comparing it to the unique uncorrelated state that has the same 1-particle density operator as does /|psi><psi/.