Detailed chemical structures and kinetics of chemical reactions at the surface and core regions of C-13 labeled atactic-poly(acrylonitrile) (aPAN) films heat-treated under air are for the first time investigated by solid-state (ss) nuclear magnetic resonance (NMR). The chemical structures of aPAN powders heat-treated under air and vacuum are also studied as reference data by ssNMR and electron spin resonance (ESR). The unpaired electron spin density is determined to be 1.43 x 10(15) and 3.30 x 10(14) spins/mg in the heat-treated powder under air and vacuum, respectively, by ESR H-1 spin-lattice relaxation time in the laboratory frame (T-1H) is 167 and 572 ms for the former and latter, respectively. A large difference in the T-1H values is attributed to differences of the unpaired electron densities. It is demonstrated that both C-13 direct polarization magic-angle spinning (DPMAS) NMR spectral patterns and T-1H values highly depend on the film thickness. Thickness dependence of apparently single T-1H values can be interpreted in terms of superposition of the short and long T-1H components at the surface and inner cores, respectively. Tunable T-1H filtered 2D C-13-C-13 through-bond correlation NMR for the first time selectively observes either well stabilized aPAN structures at the surface or poorly stabilized ones at the inner core in the films. By analyzing fully relaxed C-13 DPMAS NMR line shape, thickness of the well stabilized aPAN layer in the whole films can be estimated to be 4.5-5 mu m at heat-treatment temperature of 255 degrees C for 300 min. Moreover, kinetics of cyclization and whole stabilization processes is separately analyzed using two kinds of single-site C-13 labeled aPAN films. The complex chemical reactions of cyclization and stabilization processes in the films will be discussed in detail.