Spectroscopic Measurements of Interstellar Molecules in Astronomy

Abstract

Spectroscopic measurements of interstellar molecules are described. Since 1963 interstellar molecules have been discovered primarily by means of radio astronomical measurements, and some molecules have been detected in the infrared, optical, and ultraviolet regions. More than 120 species were detected including simple hydride, complex organic molecules, ring molecules, molecular ions, and radicals. Because of high frequency resolution fine- and hyperfine structure lines are easily observed by radio astronomical measurements, which are sometimes difficult to be resolved in ground-based laboratory measurements. Measured molecular spectra provide us with not only the precise motions of molecular clouds but excitation temperatures and molecular abundances as well. The Atacama Large Millimeter- and submillimeter Array (ALMA) is under construction in Chile through international collaboration of Japan, the US and the EU, and will soon unveil various mysteries of the universe.