Molecular Line Survey

A molecular line survey is a study of the spectrum of an astronomical source over a wide, approximately continuous, range of wavelengths, in order to determine the chemical composition and physical properties (temperature, density, internal motion) of such a region. Primarily the lower energy transitions of molecules of astrophysical interest are excited at the cold temperatures of molecular clouds, and these rotational transitions are typically at millimeter and submillimeter wavelengths (∼30–1,000 GHz), so that molecular line surveys have normally been carried out using the techniques of high-frequency radio astronomy