  It has been predicted that in the presence of a sufficiently high-dissipative
environment transport in a small tunnel junction can become extremely regular,
giving rise to the phenomenon of single-electron tunneling oscillations. Recent
progress in detection of high-frequency current fluctuations and the interest
in single-electron sources motivate further investigations on the expected
accuracy of the charge oscillations as a function of the impedance of the
environment. In this paper we study theoretically the charge-fluctuation
spectrum at finite frequency for the system at hand, and investigate its
evolution as a function of the external impedance. The evolution and the
disappearance of the single-electron oscillations peak is described by
analytical and numerical methods.
