  At the Metrology Light Source (MLS), the compact electron storage ring of the
Physikalisch-Technische Bundesanstalt (PTB) with a circumference of 48\,m, a
specific operation mode with two stable closed orbits for stored electrons was
realized by transverse resonance island buckets. One of these orbits is closing
only after three turns. In combination with single-bunch operation, the new
mode was applied for electron time-of-flight spectroscopy with an interval of
the synchrotron radiation pulses which is three times the revolution period at
the MLS of 160\,ns. The achievement is of significant importance for PTB's
future programs of angular-resolved electron spectroscopy with synchrotron
radiation and similar projects at other compact electron storage rings.
Moreover, the applied scheme for orbit and source spot selection via optical
imaging at the insertion device beamline of the MLS and may be relevant for the
BESSY VSR project of the Helmholtz-Zentrum Berlin.
