Showing papers by "Herbert Walther published in 1987"
510 citations
TL;DR: Clouds of two to about fifty simultaneously stored, laser-cooled ions in a Paul trap were observed in two phases, which are clearly distinguishable by their excitation spectra.
Abstract: Clouds of two to about fifty simultaneously stored, laser-cooled ${\mathrm{Mg}}^{+}$ ions in a Paul trap were observed in two phases, which are clearly distinguishable by their excitation spectra. Transitions between these phases can be induced either by a variation of the power of the laser radiation used to cool the ions or by a change of the size of the radio-frequency voltage applied to the trap. Transitions between a "crystalline" phase and a "gaseous" phase can be repeatedly observed by variation of the appropriate parameters. The two phases and the transitions between them have also been recorded by a photon-counting image system.
323 citations
TL;DR: The results obtained show no observable difference between normal and delayed-choice modes of operation, in agreement with the predictions of quantum mechanics.
Abstract: Following a suggestion by Wheeler, we have performed delayed-choice experiments in both the spatial and time domains. For the first experiment we use a low-intensity Mach-Zehnder interferometer, and for the second the technique of quantum beats in time-resolved atomic fluorescence. The results obtained show no observable difference between normal and delayed-choice modes of operation, in agreement with the predictions of quantum mechanics.
165 citations
TL;DR: In this article, the steady-state photon-number distribution of the microscopic maser can be recovered using the standard macroscopic quantum laser theory, and an appropriate limit of weak pump and weak photon damping is introduced to make the connection between the microscopic and the macroscope quantum theory of laser operation.
Abstract: We show that the steady-state photon-number distribution of the microscopic maser can be recovered using the standard macroscopic quantum laser theory. We introduce an appropriate limit of weak pump and weak photon damping to make the connection between the microscopic and the macroscopic quantum theory of laser operation. Simple analytic formulas describe the main features of the stationary photon-number distribution in the microscopic maser.
123 citations
TL;DR: The long lifetime of photons in a high-Q micromaser cavity is used to generate a chemically bondn>-state maser field by injecting atoms, one at a time, to calculate the probability for obtaining n photons after m atoms have passed the cavity.
Abstract: The long lifetime of photons in a high-$Q$ micromaser cavity is used to generate a $|n〉$-state maser field by injecting atoms, one at a time. Every atom is probed for its excitation after leaving the cavity so that the precise number of photons in the field is known. We calculate the probability of obtaining $n$ photons after $m$ atoms have passed the cavity.
112 citations
TL;DR: In this article, the possibility of building a free-electron laser in the spectral region of tens of nanometers using a high-power laser pulse as the undulator was discussed.
Abstract: We discuss the possibility of building a free-electron laser in the spectral region of tens of nanometers using a high-power laser pulse as the undulator. Requirements on the electron beam emittance, brightness, and energy spread are derived. The possibility of operation at the quantum limit is considered. The reduction of the gain due to diffraction of the undulator pulse (the variable mass-shift effect) is investigated, and several ways in which it could be overcome are suggested. Examples are presented showing that the device is feasible with moderate advances in current electron injector technology. Such a device would not require a large accelerator for high electron energies, nor a long wiggler made of permanent magnets.
74 citations
TL;DR: In this paper, the survival probability of the vibrational state was found to vary between 75 and 95%, depending on the surface temperature, and transfers of vibrational energy to both molecular rotation and translation were shown to be of only minor importance for vibrational relaxation during the NO/graphite interaction.
28 citations
TL;DR: In this paper, the existence of field induced bound states with a large electric dipole moment was demonstrated, where the highly excited atoms were deflected by means of an inhomogeneous electric field.
Abstract: Rydberg atoms in crossed magnetic and electric fields have been investigated. The existence of field induced bound states with a large electric dipole moment was demonstrated. For this purpose the highly excited atoms were deflected by means of an inhomogeneous electric field.
17 citations
01 Jan 1987
TL;DR: In this article, the authors reviewed single atom experiments which have been performed to demonstrate pure quantum features of the radiation field /4,6/ and showed that these properties are pure quantum effects.
Abstract: In recent years several features of the radiation field have been found which are pure quantum effects. Among these are antibunching /1/ and squeezing properties of the radiation field /2/. In addition, in quantum electrodynamics in a cavity new phenomena in the dynamics of the atom-field interaction as e.g. the collapse and revivals in the Rabi-nutation /3,4/ have been demonstrated. In this paper recent single atom experiments will be reviewed which have been performed to demonstrate pure quantum features of the radiation field /4,6/.
3 citations
01 Jan 1987
TL;DR: In this article, the authors studied the dynamics of the molecule-surface interaction in the case of molecular beam scattering from solid surfaces and combined with state-selective laser techniques for the diagnostics of the scattered molecules.
Abstract: The study of molecular beam scattering from solid surfaces /1/ combined with state-selective laser techniques for the diagnostics of the scattered molecules allows us to address some fundamental problems concerning the dynamics of the molecule-surface interaction. This problem is particularly intriguing compared to the one occurring in molecule-molecule collisions since the degrees of freedom of the two interacting partners are of fundamentally different character, individual and collective/ respectively. The way the different degrees of freedom adapt to each other during the scattering process, how they exchange energy or how they equilibrate is of paramount fundamental and technological interest. Accordingly/ in order to extract the relevant information from these investigations it is essential to maintain the specificity of each part, of the molecule as well as of the surface, in the description of the interaction and in the interpretation of the results.