Coherent hard x rays from attosecond pulse train-assisted harmonic generation.

Area of Science:

• Atomic physics
• Quantum optics
• X-ray science

Background:

• High-order harmonic generation (HHG) is a key process for producing coherent X-ray radiation.
• Relativistic effects in HHG typically hinder efficient electron recombination and harmonic emission.
• Existing methods often struggle to generate high-energy coherent X-rays.

Purpose of the Study:

• To investigate high-order harmonic generation in atomic systems under crossed relativistic laser and soft X-ray fields.
• To explore a novel method for generating coherent hard X-ray pulses.
• To overcome limitations of relativistic effects in HHG.

Main Methods:

• Theoretical consideration of atomic systems interacting with crossed laser fields.
• Utilizing a relativistically strong infrared laser field.
• Employing a weak attosecond pulse train of soft X-rays for ionization.

Main Results:

• One-photon ionization by the X-ray pulse imparts initial electron momentum.
• This momentum compensates for relativistic drift induced by the laser's magnetic field.
• Efficient electron recombination and harmonic radiation emission are achieved in the relativistic regime.

Conclusions:

• A new pathway for generating short pulses of coherent hard X-rays is demonstrated.
• The method allows for the generation of X-ray energies up to 40 keV.
• This technique offers potential for advanced applications in X-ray science and technology.