Abstract

1. In conventional optical addressing the diffraction limit λ³ selects a body about 10¹⁰ molecules to be under illumination. Out of them 10⁴ are impurities, if their relative concentration is 10^-6. Single impurity molecule spectroscopy (SMS) has to deal with one molecule at the back-ground of 10¹⁰molecules, whose frequencies are out of resonance with the excitation by a few thousands of cm^-1 (the host molecules) and 10⁴ molecules in the inhomogeneous impurity band distributed over about 1-1000 cm^-1 around the resonance. The single molecule subject to SMS (which is really a spectroscopy, not only detection) must have a sharp and intense absorption line towering well above the spectral background created by the other 10¹⁰ molecules under illumination [1,2]. The purely electronic zero-phonon line (ZPL), “the optical analog of the Mossbauer γ-resonance line” ([3] and references therein) is a proper candidate to that role.

© 1994 Optical Society of America