The structure of the nucleus 25F was investigated through in-beam {gamma}-ray spectroscopy of the fragmentation of 26Ne and 27,28Na ion beams. Based on the particle-{gamma} and particle-{gamma}{gamma} coincidence data, a level scheme was constructed
and compared with shell model and coupled-cluster calculations. Some of the observed states were interpreted as quasi single-particle states built on top of the closed-shell nucleus 24O, while the others were described as states arising from coupling of a single proton to the 2+ core excitation of 24O.
The structure of the $^{44}$S nucleus has been studied at GANIL through the one proton knock-out reaction from a $^{45}$Cl secondary beam at 42 A$cdot$MeV. The $gamma$ rays following the de-excitation of $^{44}$S were detected in flight using the 70
BaF${_2}$ detectors of the Ch^{a}teau de Cristal array. An exhaustive $gammagamma$-coincidence analysis allowed an unambiguous construction of the level scheme up to an excitation energy of 3301 keV. The existence of the spherical 2$^+_2$ state is confirmed and three new $gamma$-ray transitions connecting the prolate deformed 2$^+_1$ level were observed. Comparison of the experimental results to shell model calculations further supports a prolate and spherical shape coexistence with a large mixing of states built on the ground state band in $^{44}$S.
The structure of the weakly-bound $^{26}_{;;9}$F$_{17}$ odd-odd nucleus, produced from $^{27,28}$Na nuclei, has been investigated at GANIL by means of the in-beam $gamma$-ray spectroscopy technique. A single $gamma$-line is observed at 657(7) keV in
$^{26}_{9}$F which has been ascribed to the decay of the excited J=$2^+$ state to the J=1$^+$ ground state. The possible presence of intruder negative parity states in $^{26}$F is also discussed.
The energies of the excited states in very neutron-rich $^{42}$Si and $^{41,43}$P have been measured using in-beam $gamma$-ray spectroscopy from the fragmentation of secondary beams of $^{42,44}$S at 39 A.MeV. The low 2$^+$ energy of $^{42}$Si, 770(1
9) keV, together with the level schemes of $^{41,43}$P provide evidence for the disappearance of the Z=14 and N=28 spherical shell closures, which is ascribed mainly to the action of proton-neutron tensor forces. New shell model calculations indicate that $^{42}$Si is best described as a well deformed oblate rotor.
