Hemispherical Analyzer (HSA)
●
natural line width of the characteristic radiation used for excitation
∆
E
photo
(e.g.
Mg, K
α
, Al K
α
).
The observed total FWHM
total
is given by the convolution of the single FWHMs, e.g for
gaussian line widths.
FWHM
total
=
E
an
2
E
level
2
E
photo
2
1
/
2
=
E
(6)
FWHM
total
is usually specified using a sputter-cleaned silver sample and recording the
Ag 3d
5/2
level, after linear background subtraction. For Mg K
α
excitation, the resolution
at low HSA pass energies for the Ag 3d
5/2
level is found to be
HM
Mg K
=
0.8
eV
(7)
In most practical work, a resolution of 0.9 eV is usually sufficient for high resolution in-
vestigations. For higher instrumental resolution, it is possible to use monochromatized
X-radiation for excitation, e.g. mainly monochromatized Al K
α
radiation. For mono-
chromatized Al K
α
radiation and for the Ag 3d
5/2
level, the extreme resolution is found
to be
FWHM
extreme
=
0.44
eV
(8)
To obtain the extreme resolution of 0.44 eV, the FWHM of the X-ray has to be heavily
restricted, by utilizing only a small part of the X-ray monochromator spot area (due to
the energy dispersion across the spot area), at the expense of a strong loss in intensity.
In practice, a resolution of 0.65 eV is usually sufficient for high resolution investigations
with monochromatized Al K
α
excitation. For monochromatic radiation, FWHM
total
is
sometimes specified recording the Si 2p
3/2
level instead of the Ag 3d
5/2
level, which res-
ults in smaller values of FWHM
extreme.
due to the narrower inherent line width of the Si
2p level.
The integral signal intensity I of the measured particles (the area under the peak with a
background subtracted) is proportional to product of the accepted solid angle
Ω
S
, the
accepted sample area A
S
and the HSA resolution
∆
E
an
:
I
~
E
an
S
A
S
=
E
an
0
A
0
E
pass
E
kin
~
E
pass
2
E
kin
(9)
where
Ω
0
and A
0
are the values of the acceptances for the HSA. They are analyzer con-
stants. The equation results from Liouville’s theorem
The analyzer can be operated in two different modes:
a) Fixed Retarding Ratio (FRR), the retardation ratio R is defined as
1
For more information there are some excellent publications on analyzers. We recommend two of them:
K. D. Sevier, Low Energy Electron Spectrometry, Wiley-Interscience, 1972
D. Roy and D. Tremblay, Design of Electron Spectrometers, Rep. Prog. Phys. 53, 1621-1674,1990
19
Summary of Contents for PHOIBOS 100
Page 1: ...PHOIBOS Hemispherical Energy Analyzer Series PHOIBOS 100 PHOIBOS 150 3 1...
Page 6: ...Table of Contents PHOIBOS...
Page 10: ...Introduction 4 PHOIBOS...
Page 13: ...Electrical Connections Figure 2 Connection Scheme PHOIBOS 7...
Page 14: ...Components and Connections Figure 3 Analyzer Housing PHOIBOS100 8 PHOIBOS...
Page 15: ...Electrical Connections Figure 4 Analyzer Housing PHOIBOS150 PHOIBOS 9...
Page 42: ......
Page 51: ...SpecsLab Hardware and Software Installation PHOIBOS 45...
Page 52: ......
Page 62: ......
Page 78: ...Analyzer Checks Figure 33 Schematics of the 12 pin Analyzer Feedthrough 72 PHOIBOS...
Page 80: ......
Page 86: ......
Page 92: ...List of Figures Figure 39 Alignment Pin 84 II PHOIBOS...
Page 93: ...List of Figures PHOIBOS III...
Page 94: ......
Page 96: ......
Page 98: ...Index PHOIBOS...
