Investigation of gamma-ray fold distributions in N <= 82 Gd, Eu and Sm nuclei: Observation of a double-humped fold distribution

Cross-sections and gamma-ray fold distributions have been measured for the 97Mo+51V, 100Mo+48Ti and 114Cd+36S reactions at energies of 238, 215 and 182 MeV of the 51V, 48Ti and 36S projectiles, respectively. For the 97Mo(51V, alpha2n)142Eu reaction channel a double-humped fold distribution has been observed. This fold distribution can only be understand if an incomplete-fusion reaction mechanism associated with the alpha-particle emission is assumed. The 97Mo(51V, alpha n 143Eu reaction channel represents an incomplete-fusion reaction channel as well and its single-humped fold distribution can be described on the same footing as that of the alpha2n channel. The fold distributions associated with xn and pxn channels can be explained assuming complete-fusion reactions. For the calculations in terms of an incomplete-fusion reaction mechanism a narrow angular momentum window, ranging from ~ 68 to 82 physics planck's constant has been assumed for the 97Mo(51V, alphan) and alpha2n reaction channels. The complete-fusion reaction mechanism is considered to be negligible in this angular-momentum range.