Two-photon decay of the $2s$ state in H-like ions is investigated. We report that asymmetry in the emission of photons with left- and right-hand circular polarizations can be observed in this transition if the initial state has a certain polarization. This asymmetry can be used to measure the polarization of ion beams.Two-photon decay of the $2s$ state in H-like ions is investigated. We report that asymmetry in the emission of photons with left- and right-hand circular polarizations can be observed in this transition if the initial state has a certain polarization. This asymmetry can be used to measure the polarization of ion beams.

Physical Review AJul 1, 20210 citations

The Decay of Coupled States

Princeton University Press eBooksApr 13, 20210 citations

The grating decomposition method: A new approach for understanding polarization-selective transient grating experiments. II. Applications

John T. Fourkas, Rick P. Trebino, M. D. Fayer

We apply the theory developed in Paper I to two transient grating problems that present difficulties in interpretation and/or calculation. The first application is general, and illustrates the ability of the grating decomposition method (GDM) to facilitate calculations and to provide intuition and insight in complex orientational grating experiments: we apply the GDM to nuclear optical Kerr effect (OKE) polarization gratings. We show that the circularly polarized component gratings of the polarization-grating decomposition do not contribute to the signal, and that the OKE polarization grating can therefore be viewed as the sum of two gratings with orthogonal net molecular alignments. We also use the GDM and this system to explain why polarization gratings can rotate the polarization of the probe beam. The second example is a detailed application of the GDM to an experiment in which the data cannot be fully interpreted using standard diagrammatic perturbation methods: picosecond transient gratings on the D lines of gas-phase sodium atoms. We use the GDM and effective two-interaction matrix elements to greatly simplify this problem. We show why, in atmospheric-pressure experiments, Na intensity-grating decays are dominated by excited-state quenching, whereas Na polarization-grating decays are not. We show that the polarization-grating decays are dominated by Na diffusion and are influenced by scattering among the ground-state magnetic sublevels, but are unaffected by excited-state decay. We further show why the envelopes of polarization decays do not match the corresponding intensity-grating decays at large fringe spacings in low-pressure Na cells.We apply the theory developed in Paper I to two transient grating problems that present difficulties in interpretation and/or calculation. The first application is general, and illustrates the ability of the grating decomposition method (GDM) to facilitate calculations and to provide intuition and insight in complex orientational grating experiments: we apply the GDM to nuclear optical Kerr effect (OKE) polarization gratings. We show that the circularly polarized component gratings of the polarization-grating decomposition do not contribute to the signal, and that the OKE polarization grating can therefore be viewed as the sum of two gratings with orthogonal net molecular alignments. We also use the GDM and this system to explain why polarization gratings can rotate the polarization of the probe beam. The second example is a detailed application of the GDM to an experiment in which the data cannot be fully interpreted using standard diagrammatic perturbation methods: picosecond transient gratings on the D lines of gas-phase sodium atoms. We use the GDM and effective two-interaction matrix elements to greatly simplify this problem. We show why, in atmospheric-pressure experiments, Na intensity-grating decays are dominated by excited-state quenching, whereas Na polarization-grating decays are not. We show that the polarization-grating decays are dominated by Na diffusion and are influenced by scattering among the ground-state magnetic sublevels, but are unaffected by excited-state decay. We further show why the envelopes of polarization decays do not match the corresponding intensity-grating decays at large fringe spacings in low-pressure Na cells.

The Journal of Chemical PhysicsJul 1, 199241 citations

Decay of Atomic States

Valery S. Lisitsa

Springer eBooksJan 1, 19940 citations

Zeno and anti-Zeno effects for photon polarization dephasing

Abraham G. Kofman, Gershon Kurizki, Tomáš Opatrný

We discuss a simple, experimentally feasible scheme, which elucidates the principles of controlling the reservoir spectrum and the spectral broadening incurred by repeated measurements. This control can yield either the inhibition (Zeno effect) or the acceleration (anti-Zeno effect) of the quasiexponential decay of the observed state by means of frequent measurements. In the discussed scheme, a photon is bouncing back and forth between two perfect mirrors, each time passing a polarization rotator. The horizontal and vertical polarizations can be viewed as analogs of an excited and a ground state of a two level system (TLS). A polarization beam splitter and an absorber for the vertically polarized photon are inserted between the mirrors, and effect measurements of the polarization. The polarization angle acquired in the electrooptic polarization rotator can fluctuate randomly, e.g., via noisy modulation. In the absence of an absorber the polarization randomization corresponds to TLS decay into an infinite-temperature reservoir. The non-Markovian nature of the decay stems from the many round trips required for the randomization. We consider the influence of the polarization measurements by the absorber on this non-Markovian decay, and develop a theory of the Zeno and anti-Zeno effects in this system.We discuss a simple, experimentally feasible scheme, which elucidates the principles of controlling the reservoir spectrum and the spectral broadening incurred by repeated measurements. This control can yield either the inhibition (Zeno effect) or the acceleration (anti-Zeno effect) of the quasiexponential decay of the observed state by means of frequent measurements. In the discussed scheme, a photon is bouncing back and forth between two perfect mirrors, each time passing a polarization rotator. The horizontal and vertical polarizations can be viewed as analogs of an excited and a ground state of a two level system (TLS). A polarization beam splitter and an absorber for the vertically polarized photon are inserted between the mirrors, and effect measurements of the polarization. The polarization angle acquired in the electrooptic polarization rotator can fluctuate randomly, e.g., via noisy modulation. In the absence of an absorber the polarization randomization corresponds to TLS decay into an infinite-temperature reservoir. The non-Markovian nature of the decay stems from the many round trips required for the randomization. We consider the influence of the polarization measurements by the absorber on this non-Markovian decay, and develop a theory of the Zeno and anti-Zeno effects in this system.

arXiv:quant-ph/0011077Physical Review AMar 19, 200143 citations

Two-photon decay of the

2s

state in H-like ions is investigated. We report that asymmetry in the emission of photons with left- and right-hand circular polarizations can be observed in this transition if the initial state has a certain polarization. This asymmetry can be used to measure the polarization of ion beams.