Radio Recombination Lines: 25 Years of Investigation : Proceedings of the 125th Colloquium of the International Astronomical Union, Held in Puschino, U.S.S.R., September 11-16, 1989

Text no 1 Radio Recombination Lines (RRLs), discovered in the USSR in 1964, have become a powerful research tool for astronomers. Available throughout the radio spectrum, these lines carry information regarding the density, temperature, turbulence and velocity of thermal plasmas. Their very existance shows the presence of thermal gas. They also can carry information regarding magnetic fields if Zeeman splitting were to be detected. Containing the proceedings of an IAU Colloquium celebrating the 25th anniversary of their detection, this volume tells us what has happened since. It contains the story of the detection of RRLs and reviews of many areas of physics of the interstellargas from which stars form, HII regions excited by newly formed stars, planetary nebulae involving dying stars, and the structure of our Milky Way and other galaxies reflecting the large-scale morphology of the star formation process. In addition there is an article describing modern laboratory studies of Rydberg atoms to probe the basic physics of atomic structure, and articles describing the theory of collisions and radiation upon Rydberg atoms leading to observate effects to be used as diagnostic tools in astromony. This book focuses on the 25 years of astronomical research with radio recombination lines (RRLs) since their discovery in 1965. It covers a wide range of topics: papers dealing with research into Rydberg atoms both in the laboratory and in the interstellar medium of our galaxy and others; papers on the interaction of radiation and atomic systems, as well as with the effects of inadiabatic collisions between these atoms and both ions and electrons. It deals with astronomical observations of atoms with `diameters' ranging from 0.08 to 50 mum a size factor of 625. It deals with RRLs in absorption, in emission and as true masers. And it deals with plasmas with temperatures ranging from 10 to greater than 104 kelvins, and with an even greater range of volume densities. Much new work is reported, including low frequency RRLs discovered in 1980 and the maser RRLs from the star MWC349, discovered in 1989. The advent of aperture synthesis telescopes and large single-element telescopes have made possible RRL studies with high angular resolution. The sum total of the work reported here will make the volume a platform from which to search new horizons in RRL research. Text no 1 Radio Recombination Lines (RRLs), discovered in the USSR in 1964, have become a powerful research tool for astronomers. Available throughout the radio spectrum, these lines carry information regarding the density, temperature, turbulence and velocity of thermal plasmas. Their very existance shows the presence of thermal gas. They also can carry information regarding magnetic fields if Zeeman splitting were to be detected. Containing the proceedings of an IAU Colloquium celebrating the 25th anniversary of their detection, this volume tells us what has happened since. It contains the story of the detection of RRLs and reviews of many areas of physics of the interstellargas from which stars form, HII regions excited by newly formed stars, planetary nebulae involving dying stars, and the structure of our Milky Way and other galaxies reflecting the large-scale morphology of the star formation process. In addition there is an article describing modern laboratory studies of Rydberg atoms to probe the basic physics of atomic structure, and articles describing the theory of collisions and radiation upon Rydberg atoms leading to observate effects to be used as diagnostic tools in astromony. This book focuses on the 25 years of astronomical research with radio recombination lines (RRLs) since their discovery in 1965. It covers a wide range of topics: papers dealing with research into Rydberg atoms both in the laboratory and in the interstellar medium of our galaxy and others; papers on the interaction of radiation and atomic systems, as well as with the effects of inadiabatic collisions between these atoms and both ions and electrons. It deals with astronomical observations of atoms with `diameters' ranging from 0.08 to 50 mum a size factor of 625. It deals with RRLs in absorption, in emission and as true masers. And it deals with plasmas with temperatures ranging from 10 to greater than 10 4 kelvins, and with an even greater range of volume densities. Much new work is reported, including low frequency RRLs discovered in 1980 and the maser RRLs from the star MWC349, discovered in 1989. The advent of aperture synthesis telescopes and large single-element telescopes have made possible RRL studies with high angular resolution. The sum total of the work reported here will make the volume a platform from which to search new horizons in RRL research. Front Matter....Pages i-xi Postulation, Detection and Observations of Radio Recombination Lines (Review)....Pages 1-18 Cavity Quantum Electrodynamics: Rydberg Atoms in Atomic Physics and Quantum Optics....Pages 19-35 Review of the Populations of Highly-Excited States of Atoms in Low-Density Plasmas....Pages 37-49 The Broadening of Radio Recombination Lines by Ion Collisions: New Theoretical Results....Pages 51-57 High resolution radio recombination line observations....Pages 59-71 Radio Recombination Lines from Compact HII Regions....Pages 73-82 Radio Recombination Line Emission from Ultracompact HII Regions....Pages 83-92 Radio Recombination Lines at Millimeter Wavelengths in HII Regions....Pages 93-104 Maps of the 64α Radio Recombination Lines in Orion A....Pages 105-113 Estimate of Electron Densities in HII Regions from Observations of Pairs of α-Type Recombination Radio Lines....Pages 115-121 Interferometric Observations of HII, CII, and H° Regions in Orion B....Pages 123-130 The Helium Abundance in the HII Region DR21....Pages 131-140 Radio Recombination Lines from Stellar Envelopes: Planetary Nebulae....Pages 141-154 Radio Recombination Lines from Compact Planetary Nebulae....Pages 155-160 Radio Recombination Line Maser Emission in MWC349....Pages 161-167 Recombination emission from CII-region around Be-Stars....Pages 169-173 Review of Decameter Wave Recombination Lines: Problems and Methods....Pages 175-188 Low Frequency Radio Recombination Lines Towards Cas A....Pages 189-202 Interferometric Observations of Carbon Recombination Lines Towards Cassiopeia A at 332 MHz....Pages 203-208 Detection of Carbon Recombination Lines at Decameter Wavelengths in Some Galactic Objects....Pages 209-217 RRLs from the Local Interstellae Medium....Pages 219-224 Recombination Lines and Galactic Structure....Pages 225-236 Study of the H166α Recombination Line in the Southern Milky Way....Pages 237-248 Radio Recombination Line Imaging of Sgr A....Pages 249-258 Limits on the Temperature and Filling Factor of the Warm Ionized Medium Towards the Galactic Centre....Pages 259-265 VLA Observations of Recombination Lines from the Star Burst Galaxy NGC253....Pages 267-275 Radio Recombination Lines at 25....Pages 277-283 Back Matter....Pages 285-298