SPECS PHOIBOS Series User Manual

Spectrometer
suppressed.
3.2 Hemispherical Analyzer (HSA)
The PHOIBOS Hemispherical Analyzer (HSA) with a mean radius R
0
(100mm/150mm)
measures the energy of charged particles. Charged particles entering the HSA through
the entrance slit S1 are deflected into elliptical trajectories by the radial electrical field
between the inner hemisphere R
IN
and the outer hemisphere R
OUT
. The radii of the
PHOIBOS hemispheres are 1.25 R0 and 0.75 R0, respectively. The entrance slit S1 and exit
plane S2, are centered on the mean radius R0:
R
0
=
R
inner
 R
out
2
=150mm
(2)
For a fixed electrical field gradient, only particles with kinetic energies in a certain en-
ergy interval are able to pass through the full deflection angle from the entrance slit S1
to the exit plane S2. Particles with higher kinetic energy approach the outer hemi-
sphere, whereas particles with lower kinetic energy are deflected toward the inner
hemisphere. Those particles, which enter the HSA normal to S1 and move through the
hemispheres on the central circular trajectory, have the nominal pass energy Epass:
E
pass
=− q  k ∇ V
(3)
where q is the charge of the particle, ∆V is the potential difference Vout - Vin applied to
the hemispheres, k is the calibration constant,
k =
R
inner
R
out
2R
0
 R
out
− R
inner

=0.9375
(4)
These particles reach S2 at the nominal radial position R0. If the HSA accepts the half
angle α in the dispersion direction, the HSA resolution or FWHM (full width at half max-
imum) of the transmitted line ∆Ean is given by
 E
an
E
pass
=
S
2 R
0


2
4
(5)
where S=(S
1
+ S
2
)/2. This value is a constant of the analyzer.
There are additional contributions to the line width observed in the spectrum. For
photo-emission lines, the main additional contributions are:
● inherent line width of the atomic level ∆Elevel (e.g. O 1s, C 1s),
18 PHOIBOS

SPECS PHOIBOS Series Specifications

General

Brand	SPECS
Model	PHOIBOS Series
Category	Measuring Instruments
Language	English