Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical study of pulse delay effects in the photoelectron angular
  distribution of near-threshold EUV+IR two-photon ionization of atoms   We theoretically study the photoelectron angular distributions (PADs) from
two-color two-photon near-threshold ionization of hydrogen and noble gas (He,
Ne, and Ar) atoms by a combined action of femtosecond extreme ultraviolet (EUV)
and near-infrared (IR) laser pulses. Using the second-order time-dependent
perturbation theory, we clarify how the two-photon ionization process depends
on EUV-IR pulse delay and how it is connected to the interplay between resonant
and nonresonant ionization paths. Furthermore, by solving the time-dependent
Schr\"odinger equation, we calculate the anisotropy parameters $\beta_2$ and
$\beta_4$ as well as the amplitude ratio and relative phase between partial
waves characterizing the PADs. We show that in general these parameters notably
depend on the time delay between the EUV and IR pulses, except for He. This
dependence is related to the varying relative role of resonant and nonresonant
paths of photoionization. Our numerical results for H, He, Ne, and Ar show that
the pulse-delay effect is more pronounced for $p$-shell ionization than for
$s$-shell ionization.

9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat