A Novel Observation of "a Sharp Absorption Line" Using Much More Broad Laser Lights: Quantum Interference in the Autoionization Spectra of Sc

The most accurate measurements in physical sciences will be precision spectroscopic experiments which are based on the usage of most narrow lines in cooperation with interference phenomena. We present a novel experimental observation of ``a sharp absorption resonance line'' with much more broad laser lights. The mechanism of such a novel phenomenon will be elucidated and its implications will be discussed.