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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.Wobbling is a collective mode that may appear when the moments of inertia of all three principal axes of the nuclear density distribution are unequal. The mode is well known in classical mechanics and its occurrence is a clear signal for a triaxial nuclear shape. For a given angular momentum, uniform rotation about the axis with the largest moment of inertia corresponds to minimal energy. At a somewhat larger energy, this axis precesses (wobbles) about the space-fixed angular momentum axis. In a quantal system such as the nucleus (or a molecule), the mode manifests itself in the appearance of rotational bands that correspond to successive excitations of wobbling phonons, n ω , and alternating signature α = α 0 + n ω , which determines the spin sequence I = α + even number. Adjacent wobbling bands n ω+1 and n ω are connected by collectively-enhanced ∆I = 1 transitions of predominantly E2 character, which are generated by the wobbling motion of the entire charged body. This is in contrast with the signature-partner bands, which represent another type of excitation involving a partial dealignment of the odd particle with respect to its preferred axis; for those, the connecting ∆I = 1 transitions are of predominantly M1 character, with very little, if any, E2 admixtures.Although predicted quite sometime ago [1], this exotic nuclear motion has been observed only rarely in experiments so far, and the list of nuclei exhibiting it is quite short: 105 Pd [2], 135 Pr [3, 4] (and, possibly, 133 La [5]), 161 Lu [6], 163 Lu [7, 8], 165 Lu [9], 167 Lu [10] and 167 Ta [11]-a total of only 7(8) nuclei across the entire nuclear chart.All the aforementioned nuclei have an odd proton occu-pying a high-j orbital, which modifies the wobbling mode. Frauendorf and Dönau [12] classified this coupled mode as "longitudinal wobbling" (LW) and "transverse wobbling" (TW) when, respectively, the odd particle aligns its angular momentum along the medium axis (the axis with the largest moment of inertia), or along one of the perpendicular axes. The wobbling energy, E wobb [see Eq.(1) below], increases with increasing angular momentum for LW while it decreases for TW [12]. In all of the cases mentioned above (except, possibly, 133 La[5]), the wobbling bands have been identified as corresponding to TW because E wobb decreases with increasing angular momentum. We report on the observation of bands structures corresponding to...

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Nirupama SensharmaTriaxial nuclear shapes are a very rare phenomena that are manifested experimentally via their unique signatures -chiral rotation and wobbling motion. The present work was aimed at studying these exotic rotational modes in two different regions of the nuclear chart viz. A ∼ 130 and 190.Within the A ∼ 130 region, the primary focus of the present work was to study the 135 Pr nucleus. This nucleus was the first case of wobbling observed outside of the well-studied A ∼ 160 region. Aided with a high-statistics measurement using the Gammasphere array at the Argonne National Laboratory, the present work was able to observe a second phonon (n ω = 2) wobbling band in this nucleus. The nature of the wobbling bands was confirmed by the characteristic predominantly E2 nature of the n ω+1 → n ω linking transitions based on angular distribution measurements.3.13 Cross-sections of various residual nuclei for a 19 F beam on 174 Yb at different beam energies as calculated by PACE4. The compound nucleus produced is 193 Au which is mostly followed by the evaporation of neutrons leading to various Au isotopes.