  Background: Level structure of the most neutron deficient nucleon-bound
carbon isotope, 9C, is not well known. Definitive spin-parity assignments are
only available for two excited states. No positive parity states have been
conclusively identified so far and the location of the sd-shell in A=9 T=3/2
isospin quadruplet is not known.
  Purpose: We have studied the level structure of exotic nucleus 9C at
excitation energies below 6.4 MeV.
  Methods: Excited states in 9C were populated in 8B+p resonance elastic
scattering and excitation functions were measured using active target approach.
  Results: Two excited states in 9C were conclusively observed, and R-matrix
analysis of the excitation functions was performed to make the spin-parity
assignments. The first positive parity state in A=9 T=3/2 nuclear system, the
5/2+ resonance at 4.3 MeV, has been identified.
  Conclusions: The new 5/2+ state at 4.3 MeV in 9C is a single-particle L=0
broad resonance and it determines the energy of the 2s shell. The 2s shell in
this exotic nucleus appears well within the region dominated by the p-shell
states.
