It is well known that N=20 shell gap disappears in the "island of inversion" and thus strong deformation appears.
The one-neutron halo nucleus 31Ne, located in the island of inversion, has attracted much attention because it is the first example of a deformation-driven halo nucleus.
Recent experimental studies on 31Ne revealed that it has low separation energy Sn=0.15(+0.16)(-0.10)MeV, and ground-state spin and parity 3/2-.
These experimental results are consistent with a picture of deformed halo structure.
However the deformation has not measured directly yet.
We have performed an invariant-mass spectroscopy of 31Ne in the nuclear breakup reaction with a carbon target at ~230 MeV/u, aiming at observing its rotational band.
Additionally we also carried out a Coulomb breakup measurement with a lead target at ~230 MeV/u, in order to investigate its ground state properties.
These experiments have been done using SAMURAI spectrometer at RIBF, RIKEN.
The experimental results will be discussed in the presentation.