Lanthanides, also called rare-earth elements, are an interesting group of 15 chemically active, mainly trivalent, f-electronic, silvery-white metals. In fact, lanthanides are not as rare as the name implies, except for promethium, a radioactive artificial element not found in nature. The mean concentrations of lanthanides in the earth's crust are comparable to those of life-important elements l...

We carried out a new attempt to check for the presence promethium lines in spectrum of HD101065 (Przybylski's star). The neutron capture element does not have stable isotopes and maximum half-life time is about 18 years. Thus its this peculiar star would indicate an ongoing process irradiation surface layers with free neutrons. Unfortunately, almost all are heavily blended other elements specie...

Definitions and characteristics The rare earth elements (REE) (sometimes referred to as the rare earth metals) are a group of 17 chemically similar metallic elements, including the 15 lanthanides, scandium and yttrium. The lanthanides are elements spanning atomic numbers 57 (lanthanum, La) to 71 (lutetium, Lu) (Table 1). The lanthanides all occur in nature, although promethium, the rarest, only...