Radio-frequency Stark effect modulation of single-molecule lines

Stark effect modulation experiments were performed on single-molecule lines of terrylene in crystalline matrices of n-hexadecane and naphthalene at low temperatures. Modulation frequencies in the MHz range were used. The resulting fluorescence excitation spectra are distinctly different, depending on the relationship between the modulation frequency omega(m) and the molecular line width Gamma. For omega(m) much less than Gamma, the single-molecule line exhibits a smooth broadening and apparent splitting into two components, whereas for omega(m) much greater than Gamma it develops equidistant sidebands as in the case of phase modulation of an electromagnetic wave. It is further demonstrated that Stark effect modulation in the radio-frequency regime can be used to record absorption signals of single molecules with good signal-to-noise ratio. (C) 2000 Elsevier Science B.V. All rights reserved.