Imaging orbitals with attosecond and Ångström resolutions: toward attochemistry?

Abstract

The recently developed attosecond light sources make the investigation of ultrafast processes in matter possible with unprecedented time resolution. It has been proposed that the very mechanism underlying the attosecond emission allows the imaging of valence orbitals with Ångström space resolution. This controversial idea together with the possibility of combining attosecond and Ångström resolutions in the same measurements has become a hot topic in strong-field science. Indeed, this could provide a new way to image the evolution of the molecular electron cloud during, e.g. a chemical reaction in 'real time'. Here we review both experimental and theoretical challenges raised by the implementation of these prospects. In particular, we show how the valence orbital structure is encoded in the spectral phase of the recombination dipole moment calculated for Coulomb scattering states, which allows a tomographic reconstruction of the orbital using first-order corrections to the plane-wave approach. The possibility of disentangling multi-channel contributions to the attosecond emission is discussed as well as the necessary compromise between the temporal and spatial resolutions.

Supercontinuum in ionization by relativistically intense and short laser pulses: Ionization without interference and its time analysis

“…Along with important experimental achievements, it has led to a new branch of science called attosecond physics [7], which has already found a lot of applications in physics, chemistry, biology, and medicine. Some of these achievements are described in the review articles (see, e.g., [8][9][10][11][12][13]) or in the recent collection of articles [14] devoted to the Keldysh theory [15].…”

Time-dependent complete-active-space self-consistent-field method for multielectron dynamics in intense laser fields

“…HHG, for example, represents a highly successful avenue toward an ultrashort coherent light source in the extreme-ultraviolet (XUV) and soft x-ray regions [7,8]. The development of these novel light sources has opened new research possibilities including ultrafast molecular probing [9][10][11], attosecond science [12][13][14], and XUV nonlinear optics [15,16].…”

Influence of large permanent dipoles on molecular orbital tomography

“…This error is also observed in the previous works especially for the σ orbital. Besides the limited spectrum range, the imaging errors may also result from several other reasons, such as the discrete sampling in the frequency domain with the interval of 2ω L , and the SFA and singleactive-electron approximation used in the theoretical model [7][8][9][10]12]. In the MOT process, when the Stark phase is approximately subtracted by using the analytical expression derived in [18], the main structure of the target orbital is also successfully reproduced in both the length and velocity forms.…”

“…By applying this method to a series of aligned molecules, they accomplished a tomographic reconstruction of the highest occupied molecular orbital (HOMO) of N 2 . Since then, the MOT has attracted a great deal of attention for its great significance in uncovering the basic properties of molecules and chemical reactions [7][8][9][10][11][12][13]. In most of the works, the target molecular orbitals are symmetric with either gerade or ungerade symmetry, while the MOT of nonsymmetric orbitals is more difficult.…”