The principles involved in setting up any viable system of spectral classification are discussed. Their application is illustrated by reviewing the essential features of the original MK system of two ...

Spectral types and Hγ (W Hγ) equivalent widths have been derived from low dispersion (92 Å/mm and 51 Å/mm) spectrograms of the brightest stars in NGC 281, NGC 1893 (Aur OB 2), NGC 6823 (Vul OB 1), NGC ...

The techniques associated with these regions of the electromagnetic spectrum are probably the most widely used for analytic work. The molecular substructures that are responsible for interacting with ...

Modern instrumental chemical analysis employs a variety of techniques. Fluorescence spectroscopy is one of these methods and is based on the principle of excitation and emission of characteristic ...