Pike MIRacle ATR User Manual

PN 350-025004-09
Page | 16
Useful Equations
The depth of penetration gives us a relative measure of the intensity of the resulting spectrum and is
expressed by the following equation:
λ
2π (
n sin
2
θ
– n )
1/2
Where λ is the wavelength of light, n
1
is the refractive index of the crystal, n
2
is the refractive index of
the sample and θ is the effective angle of incidence.
Depth of penetration in microns as a function of crystal material is shown in the table below. The
penetration depth is calculated for a sample with a refractive index of 1.5 at 1000 cm
-1
. Also the safe pH
range of samples for use with each material is listed.
Materials
MIRacle
Crystal Plate
Application
Hardness
kg/mm
2
Cuttoff cm
-1
,
Spectral Range
Refractive
Index @
1000 cm
-1
Depth of
Penetration
@ 45°, µ
pH Range
of Sample
Diamond/ZnSe
Ideal for hard samples,
acids or alkaline
5700 525 2.4 2.00 1–14
Ge
General purpose and
carbon filled or rubber
550 575 4.0 0.66 1–14
Si
Excellent for far-IR spectral
measurement
1150
8900-1500,
475-40
3.4 0.85 1–12
ZnSe
General purpose ATR
crystal
120 520 2.4 2.00 5-9
NOTE:
Quoted spectral range also depends upon the FT-IR spectrometer configuration of source,
beamsplitter, detector and other components.
Zinc Selenide
ZnSe is the preferred replacement for KRS-5 for all routine applications. Its useful spectral range is less
at the low frequency end than that of KRS-5, but the mechanical strength of this rigid, hard crystalline
material is superior. Although a general-purpose material, it has limited use with strong acids and
alkalies. The surface becomes etched during prolonged exposure to extremes of pH (the acceptable pH
range is 5-9).
Note: Complexing agents, such as ammonia and EDTA, will also erode its surface because of the
formation of complexes.
d
p
=
2
1
2
2

Pike MIRacle ATR Specifications

General

Brand	Pike
Model	MIRacle ATR
Category	Accessories
Language	English