Imaging the geometrical structure of theH2+molecular ion by high-order above-threshold ionization in an intense laser field

Abstract

Using a frequency-domain theory, we demonstrate that an angle-resolved high-order above-threshold ionization ͑HATI͒ spectrum carries three pieces of important information: the fingerprint of the molecular wave function in the direct above-threshold-ionization amplitude, the geometrical structure of the molecule in the potential scattering between two plane waves, and the interaction between the ionized electron and the laser field, manifested in a phase factor associated with laser-assisted collisions. As a result all main interference features in the HATI spectrum can be physically explained. As an application it is pointed out that the skeleton structure of a molecule can be better imaged using lasers of higher frequencies.

Frequency-domain theory of nonsequential double ionization in intense laser fields based on nonperturbative QED

“…For example, HHG can be used to obtain ultrashort attosecond pulses [4,5] and to image atomic or molecular structures [6][7][8][9][10], HATI can be used to investigate molecular structures [11][12][13][14][15] and dynamics [16], and NSDI shows that the multielectron ionization in an intense laser field is not always sequentially one by one [17][18][19][20][21][22]. It is often the case that these three phenomena, i.e., HHG, HATI, and NSDI, may occur during a single recollision process, implying that we may treat them under a unified theoretical frame.…”

“…It is often the case that these three phenomena, i.e., HHG, HATI, and NSDI, may occur during a single recollision process, implying that we may treat them under a unified theoretical frame. One such approach is the frequency-domain theory based on the nonperturbative quantum electrodynamics (QED) [23], which has recently been developed to deal with recollision processes [13,15,[24][25][26][27], including HHG and HATI. By using this theory, Fu et al [25] have investigated the relationship between ATI and HHG and found that the origin of the plateau on a HHG spectrum is attributed to a laser-assisted recombination process.…”

“…By using this theory, Fu et al [25] have investigated the relationship between ATI and HHG and found that the origin of the plateau on a HHG spectrum is attributed to a laser-assisted recombination process. Recently, Guo et al [13] have investigated the interference fringes in the HATI spectra of molecules and found the charge distribution effect of imaging the molecular structure by HATI [15].…”

“…Consequently, the characteristics of a recollision process lay in the LAC or LAR, with a weight given by the first-step ATI transition. For example, the quantum interference fringes in an angle-resolved HATI spectrum of a diatomic molecule are attributable to the two-center LAC and the oscillation of recolliding electrons driven by the laser [13]. In this paper, we will develop this method to investigate the NSDI process.…”

Extracting the information of scattering potential using angular distributions of rescattered photoelectrons

“…The photoelectrons arising from the rescattering process have much higher kinetic energy-up to about 10U p -since they are further accelerated by the electric field. More importantly, the rescattered photoelectrons carry information about the potential of their parent core, thus providing a supplementary means to learn about the core structure of the target atoms and molecules [5][6][7].…”