Definition of Pump-Probe techniques

[kara-mela]

HZDR is interested in adding their pump-probe techniques to PaNET. This caused an intensive discussion during the PaNET meeting on 2026-06-25.

This issue will cover or at least initiate the following steps:

1. summarize the thoughts of the initial discussion.
2. more detailed discussions on a conceptual definition of pump-probe experiments in general.
3. Integreate pump-probe experiments to PaNET, including possible schema changes.

[kara-mela]

Summary of the discussion from 2026-06-2

Definition

• pump activates something within the sample, the decay is monitored by the probe

Purpose of Pump-Probe Experiments

• more than one purpose can be assigned
• example: EXAFS and XANES; identical technique, but different data analysis reveals different sample properties (purposes)

Collaboration

• similar experiments performed at ELI -> joint discussions

Pump as Dependency -- Comparison to in-situ/operando

• What does dependency refer to?
  • a static, characteristic of sample?
  • you have a parameter and watch the sample while this parameter is changing; signal as function of this parameter
    • comment: what about experiments that are performed at a constant but non-ambient conditions (e.g. sample constant 100°C)
    • the experiment could depend on the power of the pump, its duration, its energy
    • pump is a transient property
  • referring to static (long-term) or transient (short-term) dependency? or both?
• good fit for neutron pump-probe experiments (measure, break, measure, break) In those breaks, shine a laser beam onto the sample, before next probe, similar as changing temperature
• rough definition of in-situ/operando
  • in-situ: sample in a specific "situation"/condition other than ambient
  • operando: subgroup of in-situ; sample is a (piece of) technical device analyzed under (near) operation conditions) -- WE SHOULD NOT FOCUS ON OPERANDO IN PaNET
  • both describe experiments under non-ambient, constant or varying conditions, thus depending on an external parameter
• pump as a group of dependencies?
• main purpose: altering sample

Pump as 2nd kind of Probe

• pump signal is often a laser pulse, basically photons with intensity and energy, highly similar to a probe in PaNET
• pump is extra condition you need to apply in order to perform the experiment, new fundamental (optional) dimension
• for (most) experiments/measurement: probe should not alter the sample, BUT the pump is especially designed to alter the sample
  • comment: in addition to classical experiments/measurements, PaNET also covers manufacturing, therapy, and testing purposes (see Restructuring "defined by purpose" terms #277). In therapy and manufacturing, the altering of the sample are in fact desired.
• distinction between probe and pump: timing of data taking, which is synchronized with probe rather than pump
• main purpose of probe: analyzing sample
  • see previous comment

Temporal Development

• current technique definition in PaNET is static. do we need to extend it by temporal development?

"Conditioning of the Sample"

• new main category of PaNET?
• as superclass of defined by dependence and pump-probe?

Side notes

• There is something wrong with ultrafast probe.
  • Status:
    • ultrafast probe-based techniques is subclass of defined by experimental probe
    • ultrafast probe is subclass of pulsed probe
    • pulsed probe is subclass beam characteristic
  • Suggestion: This implies that ultrafast techniques inherit from probe and from beam characteristic, which should not be the case. In fact, ultrafast is rather a beam characteristic than a probe.
  • Definition: ultrafast refers to duration of pulses not frequencies