Abstract
Gamma ray pulsars have been long studied ever since their discovery. A two-layer outer gap model is now used to explain the high energy emission, spectral properties and light curves of pulsars. This model describes the outer gap as a region consists of two parts, the acceleration region and the screening region. In the accelerating region the the charge density is very low and the charged particles can be accelerated to relativistic velocity along the magnetic field and emit high energy photons and in the screening region the charge density is high and the gap is closed. A three-dimensional two-layer outer gap model with an azimuthal structure was previously proposed to explain the energy-dependent third peak of Vela pulsar by Fermi observation, which fitted well to the observation. This model is now being applied to other pulsars, compare their model phase-averaged spectrum, phase-resolved spectrum and light curves with the observations, and the results show that the spectra are well fitted either under the cutoff energy or above, but not in the entire energy band from 100MeV to 300GeV. It is suggested that a weighting factor should be assigned to one of the main parameters that indicates the size of the gaps, and a distribution can be given to such parameter, which improved the model fitting results. This is probably caused by the time-dependent structure of the outer gaps which is not considered in the current model, which is the next step of this research work.