We present here the coupling of a flash pyrolysis micro-reactor with threshold photoelectron photoion coincidence (TPEPICO) spectroscopy at Hefei synchrotron to investigate thermal decomposition of n-butane. Primary products in the pyrolysis were determined with TPEPICO time-of-flight mass spectra and mass-selected threshold photoelectron spectra (TPES). Vibrational structures in the TPES of the CH3, C2H5 and C3H6 products were observed and their ionization energies were measured and compared satisfactorily to literature data. Moreover, the potential energy surface involved in the decomposition was calculated by using high-level quantum chemistry and several transition states were recognized. Then the detailed mechanisms of the pyrolysis of n-butane have been discussed and revealed.
