Biomedical subjects

T R Geballe

Publications and source records attributed to T R Geballe.

3 recordsLinked to original sources

PubMed1998

Detection of H3+ in the diffuse interstellar medium toward Cygnus OB2 No. 12.

The molecular ion H3+ is considered the cornerstone of interstellar chemistry because it initiates the reactions responsible for the production of many larger molecules. Recently discovered in dense molecular clouds, H3+ has now been observed in the diffuse interstellar medium toward Cygnus OB2 No. 12. Analysis of H3+ chemistry suggests that the high H3+ column density (3.8 x 10(14) per square centimeter) is due not to a high H3+ concentration but to a long absorption path. This and other work demonstrate the ubiquity of H3+ and its potential as a probe of the physical and chemical conditions in the interstellar medium.

Astronomical Phenomena↗

PubMed1998

H3+ in dense and diffuse clouds.

Interstellar H3+ has been detected in dense as well as diffuse clouds using three 3.7 microns infrared spectral lines of the nu 2 fundamental band. Column densities of H3+ from (1.7-5.5) x 10(14) cm-2 have been measured in dense clouds in absorption against the infrared continua of the deeply embedded young stellar objects GL2136, W33A, MonR2 IRS 3, GL961E, and GL2591. Strong and broad H3+ absorptions have been detected in dense and diffuse clouds towards GC IRS 3 and GCS3-2 in the region of the galactic center. A large column density of H3+, comparable to that of a dense cloud, has been detected towards the visible star Cygnus OB2 No. 12, which has a line of sight that crosses mostly diffuse clouds. The H3+ chemistry of dense and diffuse clouds are discussed using a very simple model. Some future projects and problems are discussed.

Astronomical Phenomena↗

PubMed1996

Detection of H3+ in interstellar space.

The H3+ ion is widely believed to play an important role in interstellar chemistry, by initiating the chains of reactions that lead to the production of many of the complex molecular species observed in the interstellar medium. The presence of H3+ in the interstellar medium was first suggested in 1961, and its infrared spectrum was measured in the laboratory in 1980. But attempts to detect it in interstellar space have hitherto proved unsuccessful. Here we report the detection of H3+ absorption in the spectra of two molecular clouds. Although the present results do not permit an accurate determination of the H3+ abundances, these ions appear nevertheless to be present in sufficient quantities to drive much of the chemistry in molecular clouds. It should soon be possible to obtain more accurate measurements, and thus better quantify the role of ion-neutral reactions in the chemical evolution of molecular clouds.

Extraterrestrial Environment↗