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SUMMARY:Thermodynamics\, phonon occupation numbers\, and their measurement
 s by helium spin echo - Dr Boyao Liu\, Cavendish Laboraroty\, University o
 f Cambridge
DTSTART:20250819T130000Z
DTEND:20250819T140000Z
UID:TALK235243@talks.cam.ac.uk
CONTACT:Boyao Liu
DESCRIPTION:In this seminar\, we begin with fundamental principles of ther
 modynamics to establish the energy distribution of a harmonic oscillator a
 t constant temperature\, which corresponds to the Bose–Einstein distribu
 tion. We then introduce helium spin echo (HeSE) spectroscopy as a powerful
  technique for probing phonons at surfaces. We will show that HeSE provide
 s access to the differential scattering cross section of helium atoms inte
 racting with a sample surface. From the differential scattering cross sect
 ion\, the Debye–Waller factor of diffuse elastic scattering can be extra
 cted. Furthermore\, by comparing the relative intensities of the elastic p
 eak and the one-phonon inelastic peak\, the Bose–Einstein distribution o
 f surface phonons can be experimentally determined.
LOCATION:D2.002\, Ray Dolby Centre\, Cavendish Laboratory
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