  Pulsed electrostatic gating combined with capacitive charge sensing is used
to perform excited state spectroscopy of an electrically isolated
double-quantum-dot system. The tunneling rate of a single charge moving between
the two dots is affected by the alignment of quantized energy levels; measured
tunneling probabilities thereby reveal spectral features. Two pulse sequences
are investigated, one of which, termed latched detection, allows measurement of
a single tunneling event without repetition. Both provide excited-state
spectroscopy without electrical contact to the double-dot system.
