total number of wires acting in the wire frame; this therefore has to be of substancial is the use of delicate wires and the wire stretching force, which is proportional to the and it operates in a stable fashion for long irradiation periods. The drawback here spatial resolution. In addition it can achieve higher electron multiplication factors performance of this structure equals that of the MSGC in terms of rate capability and to the cathode plane with engraved pick-up strips orthogonal to the wire direction. The multiwire structure [7,8] with alternating anodes and field-shaping wires, mounted close Another possible way out is the use of a special asymmetric configuration of the and spatial resolution.resolve the charging~up problem and giving superior results in terms of rate capability this class of gas detectors, the micro-gap chamber [6], was recently developed aiming to the resistivity of the substrate or a special treatment of its surface. Another type in during the last few years, to resolve the charging-up problem by a careful choice of of the gain in the irradiated area of the detector [5]. A lot of effort has been invested, and accumulated on the insulator, locally modify the electric field and cause a drop breakdown on the insulator surface. Positive ions created during the avalanche process detector is the fact that the avalanche multiplication does not exceed 104, because of offers the possibility to cope with higher counting rates. One limitation of the MSGC allows a good spatial resolution, inferior to 100 ps and the fast collection of the charges of gas detector relying on the microelectronics technology. The small inter-strip pitch tion, is created between the thin cathode and anode conductive strips. It is a new class on an insulating support; a high electric field region, sufhcient for electron multiplica has been developed over the last eight years [2,3, 4]. Wires are replaced by strips printed To overcome these limitations, a new technique, the microstrip gas chamber (MSGC), of 1 mm.onds. Their spatial resolution was limited by the wire spacing, which was of the order cause of the low ion drift velocity with a typical drift time of several tenths of microsec Their flux capability was mainly limited by the positive-ion space charge created be Multiwire proportional chambers have been originally designed for high-rate applicati0ns [1].

Atomic interferometry was born recently, towards the end of the 1980s. Its development has been extremely fast, new techniques being pioneered independently and almost simultaneously in different laboratories all over the world. Nowadays, these techniques have reached a high level of sophistication, opening a wide area of fundamental and practical applications. In this paper the general architecture of interferometers in which matter waves are coherently manipulated is described. Various realizations of atom and molecule interferometers are reported, together with the major results obtained with each type of interferometer. Finally, new trends and perspectives are given. Whilst the techniques seem to be almost completely achieved, new developments are coming up, such as the use of new and non-ordinary sources. Forthcoming applications are numerous. They deal with the most fundamental aspects of quantum mechanics, with the metrology of fundamental constants, with the use of interferometers as very sensitive probes of external interactions and inertial effects, with atomic nanolithography, etc.

A new potential energy surface for the electronic ground state of the simplest triatomic anion H(3) (-) is determined for a large number of geometries. Its accuracy is improved at short and large distances compared to previous studies. The permanent dipole moment surface of the state is also computed for the first time. Nine vibrational levels of H(3) (-) and 14 levels of D(3) (-) are obtained, bound by at most approximately 70 and approximately 126 cm(-1), respectively. These results should guide the spectroscopic search of the H(3) (-) ion in cold gases (below 100K) of molecular hydrogen in the presence of H(-) ions.