Dear Murpholino,
Interaction of waves and matter always involve the particle-wave
duality. Some pocesses are easier described using particles, others by
using the wave concept.
The X-ray photon, or rather the X-ray wavelet, has only a small chance
of "hitting" atoms in the crystal. We will use the wave concept as the
X-ray is interacting with all atoms in the crystal over a given
coherence length. The energy of the wavelet is tranferred to electrons
in the atoms elastically, and they will start oscillating with the same
frequency as the X-ray wave. Thereby they emit X-radiation (again with
the same frequency) in all directions (more in directions perpendicular
to the oscillation direction = polarization). The electromagnetic waves
of the electrons/atoms have constructive interference in directions
caused by the three periodic axes in the crystal (i.e. what we call
diffraction).
Best wishes,
Loes
On 05/22/15 03:43, Murpholino Peligro wrote:
Hello Everybody!
I was trying to make some sense from Bernhard Rupp's book page 251.
I will copy the relevant part...
When photons travel through a crystal, either of two things can
happen: (i) nothing, which happens over 99% of the time; (ii) the
electric field vector induces oscillations in all the electrons
coherently within_the photon's coherence length_ ranging from a few
1000 Angstroms for X-ray emission lines to several microns for modern
synchrotron sources. At this point, the photon ceases to exist, and we
can imagine that the electrons themselves emanate _virtual waves_,
which constructively overlap in certain directions, and interfere
destructively in others. The scattered photon then _appears again in
some direction_, with the probability of that appearance proportional
to the amplitude of the combined, resultant scattered wave in that
particular direction.......The sum of all scattering events of
independent, single photons then generates the diffraction pattern.
I underlined the problematic parts...
can anyone shed some light on this ..or point me in the right direction?
Thanks in advance
--
__________________________________________
Dr. Loes Kroon-Batenburg
Dept. of Crystal and Structural Chemistry
Bijvoet Center for Biomolecular Research
Utrecht University
Padualaan 8, 3584 CH Utrecht
The Netherlands
E-mail : [email protected]
phone : +31-30-2532865
fax : +31-30-2533940
__________________________________________
