Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multiphoton transitions for delay-zero calibration in attosecond
  spectroscopy   The exact delay-zero calibration in an attosecond pump-probe experiment is
important for the correct interpretation of experimental data. In attosecond
transient absorption spectroscopy the determination of the delay-zero
exclusively from the experimental results is not straightforward and may
introduce significant errors. Here, we report the observation of
quarter-laser-cycle (4{\omega}) oscillations in a transient absorption
experiment in helium using an attosecond pulse train overlapped with a
precisely synchronized, moderately strong infrared pulse. We demonstrate how to
extract and calibrate the delay-zero with the help of the highly nonlinear
4{\omega} signal. A comparison with the solution of the time-dependent
Schr\"odinger equation is used to confirm the accuracy and validity of the
approach. Moreover, we study the mechanisms behind the quarter-laser-cycle and
the better-known half-laser-cycle oscillations as a function of experimental
parameters. This investigation yields an indication of the robustness of our
delay-zero calibration approach.

12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: econ
22
The categories of this paper are: chao-dyn