[en] Am-Be radioactive sources are commonly used in laboratory as easy source for fast neutron generation. It can also be used as a mono energetic 4.4 MeV energy gamma ray source. The α-particle, from ²⁴¹Am, captured by ⁹Be nucleus produces neutrons and higher energy gamma rays, via reaction ⁹Be(α,n)¹²C. Due to the source composition matrix effects in alpha energy loss, and multiple scattering of neutrons inside the source, the emitted neutrons are having a continuous energy. To understand the exact nature of neutron spectrum, the individual neutron colonies corresponding to residual energy states of ¹²C has to be correlated through the level scheme of ¹²C. With this motivation, the neutron spectrum from a 100mCi Am-Be source has been measured using time of flight (TOF) setup, gating the gamma rays from different decay levels of residual ¹²C states