The interaction of resonant radiation with atoms or molecules present in a discharge can induce variation in the electrical properties of the discharge. This effect, known as the optogalvanic effect, has been shown to be a powerful and inexpensive technique for the investigation of atomic and molecular species. Many theoretical and experimental articles have been published in the last ten years on this subject. In this review the different types of optogalvanic techniques that have been developed are reviewed and the principal theoretical models are analyzed. The spectroscopic applications are examined. An extensive reference list is included, providing an overview of the literature.

We propose an underground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de~Sitter effect) and to the rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a triaxial laser detector of rotation. The proposed detector consists of six large ring lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6~m side, assuming a shot noise limited sensitivity (20\,\,prad/s/Hz). The multigyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedral structures. It is shown that the symmetries of the proposed configurations provide mathematical relations that can be used to ensure the long term stability of the apparatus.

The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deep waters of the Mediterranean Sea. This digital optical module has a novel design...

We have measured the hyperfine relaxation time of cesium vapor in the presence of foreign gases. We have therefore been able to measure the diffusion coefficient $D_0$ and the cross section $\sigma 〈\overrightarrow{\mathrm{S}}·\overrightarrow{\mathrm{I}}〉$ of hyperfine relaxation due to the collisions with the foreign gas. The values of $D_0$ for He, Ne, Ar, and ${\mathrm{N}}_2$ are 0.204±0.04, 0.153±0.014, 0.134±0.02, and 0.073±0.015 ${\mathrm{cm}}^2$/sec at 0°C and 760 Torr, respectively. The cross sections are 2.80±0.3, 9.27±0.9, 104±10, and 55.2±4.4 in units of ${10}^{-23\mathrm{}}$ ${\mathrm{cm}}^2$ for He, Ne, Ar, and ${\mathrm{N}}_2$, respectively. We have also improved on the measurement of the spin-exchange cross section ${\sigma }_{\mathrm{ex}}$ obtaining the value (2.18±0.12)×${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^2$. We compare the problems arising in the study of hyperfine and Zeeman relaxation and we discuss the results.

GINGERino is a large frame laser gyroscope investigating the ground motion in the most inner part of the underground international laboratory of the Gran Sasso, in central Italy. It consists of a square ring laser with a 3.6 m side. Several days of continuous measurements have been collected, with the apparatus running unattended. The power spectral density in the seismic bandwidth is at the level of ${10}^{-10}\hspace{0.17em}(\text{rad}/\text{s})/\sqrt{\text{Hz}}$ . A maximum resolution of $30\hspace{0.17em}\text{prad}/\text{s}$ is obtained with an integration time of few hundred seconds. The ring laser routinely detects seismic rotations induced by both regional earthquakes and teleseisms. A broadband seismic station is installed on the same structure of the gyroscope. First analysis of the correlation between the rotational and the translational signal is presented.