Measurement of proton-distribution radii of neutron-rich nitrogen isotopes

Measurement of root-mean-square radii of proton distributions of 17–22 N from charge-changing cross section shows the emergence of thick neutron skin towards the neutron-drip line. Signature of N = 14 shell gap has been found in nitrogen isotopes along with the emergence of neutron halo in 22 N. The measured radii are in good agreement with the shell model calculations.