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C60 cluster thin films were obtained by thermal evaporation under argon atmosphere. The surface morphology, optical absorption characteristics and structure of these films have been investigated. The ultraviolet-visible optical absorption spectrum of this C60 film is obviously different from that of the film obtained under vacuum conditions. The position and intensity of absorption peaks of the films grown in argon are modified compared with the film grown in vacuum. The bandgap energy changes from 2.02 eV to 2.24 eV. IR analyses show no evidence of chemical change. The x-ray diffraction pattern reveals the existence of a mixture of face-centred cubic and hexagonal close-packed phases. The collisions of C60 molecules and buffer gas molecules are discussed. We also found the surface particles of these C60 cluster films are larger and sharper than those of C60 films prepared in vacuum by the observation of atomic force microscopy (AFM). This may be advantageous for using C60 for electron field emission.

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Long-time coherent integration works to significantly increase the detection probability for maneuvering targets. However, during the observation time, the problems that often tend to occur are range cell migration (RCM) and Doppler frequency cell migration (DFCM), due to the high velocity and acceleration of the maneuvering target, which can reduce the detection of the maneuvering targets. In this regard, we propose a new coherent integration approach, based on the product scale zoom discrete chirp Fourier transform (PSZDCFT). Specifically, by introducing the zoom operation into the modified discrete chirp Fourier transform (MDCFT), the zoom discrete chirp Fourier transform (ZDCFT) can correctly estimate the centroid frequency and chirp rate of the linear frequency-modulated signal (LFM), regardless of whether the parameters of the LFM signal are outside the estimation scopes. Then, the scale operation, combined with ZDCFT, is performed on the radar echo signal in the range frequency slow time domain, to remove the coupling. Thereafter, a product operation is executed along the range frequency to inhibit spurious peaks and reinforce the true peak. Finally, the velocity and acceleration of the target estimated from the true peak position, are used to construct a phase compensation function to eliminate the RCM and DFCM, thus achieving coherent integration. The method is a linear transform without energy loss, and is suitable for low signal-to-noise (SNR) environments. Moreover, the method can be effectively fulfilled based on the chirp-z transform (CZT), which prevents the brute-force search. Thus, the method reaches a favorable tradeoff between anti-noise performance and computational load. Intensive simulations demonstrate the effectiveness of the proposed method.