Single-hemisphere photoelectron momentum microscope with time-of-flight recording

Area of Science:

• Surface Science
• Condensed Matter Physics
• Spectroscopy

Background:

• Photoelectron momentum microscopy is a powerful technique for angle-resolved photoelectron spectroscopy (ARPES).
• Existing methods often use double-hemispherical or time-of-flight (ToF) energy filters.
• Current instruments typically record kx-ky images within a single Brillouin zone.

Purpose of the Study:

• To introduce a novel approach for mapping the full half-space momentum.
• To demonstrate enhanced energy and angular resolution in photoelectron spectroscopy.
• To develop a method overcoming limitations in time-resolved ARPES experiments.

Main Methods:

• Utilized a large single hemispherical analyzer (225 mm path radius) for momentum mapping.
• Employed a He lamp for excitation, achieving 7.7 meV energy resolution.
• Introduced a dispersive-plus-ToF hybrid mode for 3D data acquisition (EB, kx, ky).

Main Results:

• Successfully performed k-imaging of quantum-well states in Au and Xe multilayers.
• Studied α²-aberration and transit-time spread over a wide pass-energy and angular range.
• Demonstrated numerical correction of detrimental aberration and spread effects for time-resolved studies.

Conclusions:

• The new method enables full half-space momentum mapping with high resolution.
• The dispersive-plus-ToF hybrid mode significantly enhances recording efficiency (up to N²).
• This technique is crucial for ARPES at high-pulse-rate sources like synchrotrons.