Nonsequential double ionization of atoms driven by spatially inhomogeneous laser fields

Using a three-dimensional classical ensemble method, we investigate the nonsequential double ionization (NSDI) of xenon atoms from the near infrared wavelength to the mid-infrared wavelength in spatially inhomogeneous laser fields, and compare the results with those from spatially homogeneous laser fields. The results show that the NSDI probability curves from spatially inhomogeneous laser field and spatially homogeneous laser field at short wavelength are similar to each other. With the laser wavelength increasing, NSDI at the high intensities is more and more suppressed for spatially inhomogeneous laser field. Compared with the result from the spatially homogeneous laser field, the final emission angle of two electrons from the NSDI exhibits a very strongly correlated characteristic in the spatially inhomogeneous field, especially at a longer laser wavelength, the final emission angles of two electrons are almost both concentrated around, meaning that the two electrons are always emitted into the same direction parallelly. Moreover, effective recollision of the NSDI is always dominated by first return of the first electron from the near infrared to the mid-infrared inhomogeneous laser fields, however, the transition from the first return dominance to the second return dominance occurs in the spatially homogeneous laser fields. Further, we reveal the more details of the ultrafast dynamics of the correlated electrons in the spatially inhomogeneous laser field by back-tracing the classical trajectories of NSDI.