Tunnelling Dynamics With Optical Field Manipulation

Recent advances in the technology of optical field manipulation have opened up unprecedented opportunities for steering and tracking of the atomic-scale motion of electrons.Extracting the temporal and spatial information embedded in the observed experimental phenomena is one of the research hot subjects in strong-field physics and attosecond science.Tunnelling lies at the heart of quantum mechanics and is a fundamental process in attosecond science,molecular biology,and quantum devices.How a microscopic particle tunnels through a barrier has been debated since the early days of quantum mechanics.This dissertation mainly conducts Stark shift and tunnelling time in the tunnelling dynamics of the Xe atom with optical field manipulation.The main innovative results are as follows:Firstly,an improved quantum trajectory Monte Carlo method including the Stark shift in tunnelling dynamics,Coulomb potential,and multielectron polarizationinduced dipole potential is adopted to revisit the origin of the low energy interference structure in the photoelectron momentum distribution of the xenon atom subjected to an intense laser field,and resolve the different contributions of these three effects.We found that the Stark shift plays an essential role on the low-energy interference structure,which moves the ringlike constructive interference structure to the lower momentum region.The formation of the low-energy interference structure is a result of the combined effects of Stark shift,laser,and Coulomb fields,while the multielectron polarization mainly enhances the probability of the low energy photoelectron spectrum.Our finding provides insight into the electron dynamics of atoms and molecules when driven by the intense laser fields.Secondly,the time required for an electron to tunnel through an atomic potential barrier has been measured with attosecond angular streaking(attoclock),and a recent work on the hydrogen atom claimed that electron tunnelling is instantaneous.However,the time required for Rb atoms to tunnel through an optical potential barrier has been measured to be on the order of milliseconds with a recent Larmor clock measurement.The essence of electron and atom tunnelling is identical,but the reason for the contradictory conclusions remains unknown.Here,we demonstrate that the sub-barrier potential interaction is the root of the nonzero tunnelling delay time.We reveal that the wave-particle duality of a tunnelling electron must be fully taken into account when decoding the tunnelling delay time from the attoclock measurements.Based on energyresolved attoclock measurements,we show that the tunnelling delay time of an electron ranges from 24 to 58 attoseconds,and the counterintuitive result that an electron with a lower energy may spend less time in the barrier is consistent with the velocitydependent tunnelling time of atoms in Larmor clock measurements Our results unify the tunnelling time of microscopic particles by highlighting the classically forbidden sub-barrier potential interactions of matter waves.