The time-evolution operator for an explicitly time-dependent Hamiltonian is expressed as the product of a sequence of unitary operators. These are obtained by successive time-dependent unitary transformations of the Hilbert space followed by the adiabatic approximation at each step. The resulting adiabatic product expansion yields a generalization of the quantum adiabatic approximation. Further...

The Swift satellite early X-ray data show a very steep decay in most of the gamma-ray bursts light curves. This decay is either produced by the rapidly declining continuation of the central engine activity or by some leftover radiation starting right after the central engine shuts off. The latter scenario consists of the emission from an ‘ember’ that cools via adiabatic expansion and, if the je...

The cooling of molecules during the adiabatic expansion of supersonic seeded molecular beams is reviewed and illustrated by the example of NO -molecules. The reduction of the Doppler width by collimation of the beam and the cooling to low rotational temperatures brings a significant simplification of the complex NO -absorption spectrum and allows its assignment. The measured rotational tem...