  The rare phenomenon of nuclear wobbling motion has been investigated for the
nucleus $^{187}$Au. A longitudinal wobbling-bands pair has been identified and
clearly distinguished from the associated signature-partner band on the basis
of angular distribution measurements. Theoretical calculations in the framework
of the Particle Rotor Model (PRM) are found to agree well with the experimental
observations. This is the first experimental evidence for longitudinal wobbling
bands where the expected signature partner band has also been identified, and
establishes this exotic collective mode as a general phenomenon over the
nuclear chart.
