An analytical solution for the time evolution of decay of two identical non interacting quantum particles seated initially within a potential of finite range is derived using the formalism of resonant states. It is shown that the wave function, and hence also the survival and nonescape probabilities, for factorized symmetric and entangled symmetric/antisymmetric initial states evolve in a distinctive form along the exponentially decaying and nonexponential regimes. Our findings show the influence of the Pauli exclusion principle on decay. We exemplify our results by solving exactly the s-wave delta shell potential model.Comment: 14 pages, 3 figures, added references and discussio

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Rotational wave packets of the weakly bound C 2 H 2 -He complex have been created using impulsive alignment. The coherent rotational dynamics were monitored for 600 ps enabling extraction of a frequency spectrum showing multiple rotational energy levels up to J ¼ 4. spectrum has been combined with ab initio calculations to show that the complex has a highly delocalized structure and is bound only by ca. 7 cm −1 . The experiments demonstrate how highly featured rotational spectra can be obtained from an extremely cold environment where only the lowest rotational energy states are initially populated. DOI: 10.1103/PhysRevLett.113.043004 PACS numbers: 33.20.-t, 33.80.-b, 36.40.Mr Weakly bound molecular complexes are important model systems for condensed matter held together by van der Waals forces [1]. The weak binding leads to large amplitude motion and delocalized structures that are often reflected in complex rotational spectra that cannot easily be categorized through rigid rotor models. Furthermore, obtaining these spectral features imposes practical problems associated with the very low temperatures that are required to form weakly bound complexes. The low temperatures imply the population of only the lowest quantum states. Consequently, the features in conventional rotational (microwave) spectroscopy comprise only a few lines-often not enough for a comprehensive analysis of the structure of the complex [2].A potential solution to this problem is to use impulsive alignment to generate rotational wave packets through the nonresonant interaction of an intense laser field with a molecule, aligning it in space [3]. Tuning the laser pulse duration and intensity controls the number of rotational eigenstates that contribute to the wave packets. Using this technique for isolated molecules it is possible to monitor the evolution of alignment in time, simultaneously obtaining information on the rotational dynamics and structure [3][4][5][6][7][8][9][10]. The extension of this technique to complex systems where weak interactions are important has been postulated theoretically [11], and demonstrated on the very simplest of systems, noble-gas dimers [12]. The extension of impulsive alignment to van der Waals complexes with internal and delocalized structures remains a challenge. This is due in part to the weak binding and floppy nature of the complex, but also due to the increased complexity of the resulting rotational spectrum, such that currently, to the best of our knowledge, no such measurement has been reported.This approach may also have potential for exploring liquids, where the wave-packet dynamics will be sensitive to dephasing. A particularly promising liquid to begin such studies is superfluid helium. Frequency-domain spectra of molecules embedded into large superfluid helium droplets show sharp rotational transitions, suggesting that wave packets will not dephase [2,13]. However, the recent attempt to impulsively align molecules in large helium droplets by Pentlehner et al. suggests that this may not be th...

Positively charged helium clusters, also called 'snowballs', have been investigated within normal liquid helium. Thermodynamic state equations for ionic helium clusters in liquid helium have been developed, allowing us to discern the 'hydrodynamic' radius for a wide range of hydrostatic pressures and temperatures. The mobilities derived from the cluster sizes using Stokes law match experimental data with unsurpassed accuracy. For low pressures the compressibility of the cluster ions was found to be distinctly larger than the compressibility of solid helium suggesting that in this pressure range clusters are fully or partially liquid.

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