Overview
For experiments on electron spin resonance in conjunction with the ESR control unit (514 57) or the ESR adapter (514 56).
Technical Data
•Power supply: 12 V; 175 mA
•Frequency range of each coil:
approx. 13 to 30 MHz,
approx. 30 to 75 MHz,
approx. 75 to 130 MHz
•Voltage at RF coil:
approx. 6 Vpp (with respect to earth) at 13 MHz
and max. amplitude setting
•ESR signal:
approx. 1 to 6 V (frequency dependent)
•Frequency divider: 1000 : 1
•Frequency response for digital counter: TTL
•Resonance meter current (DC):
approx. 100 µA
•Frequency range of the passive
resonant circuit: 10 to 50 MHz
•Dimensions of the probe head:
13 cm · 7 cm 4 cm
•Stand length: 18.5 cm
•Weight: approx. 0.7 kg
Scope of delivery
1 ESR probe head (variable high-frequency transmitter, frequency divider and low-frequency signal amplifier)
3 Plug-in coils for different frequency ranges
1 Measuring cable, for employing the unit as a resonance meter
1 Passive electric resonant circuit for investigating the dependence of the resonant frequency on the magnetic field
1 DPPH-probe (diphenyl-picryl-hydrazyl)
Description
The magnetic moment of the unpaired electron with the total
angular momentum j in a magnetic field assumes the discrete
energy states
Em = � gj � BB � m � B where m = �j, �j + 1, ... , j
BB = 9,274 � 10�24 J
: Bohr�s magneton
T
gj: g factor
When a high-frequency magnetic field with the frequency V is
applied perpendicularly to the first magnetic field, it excites transitions
between the adjacent energy states when these fulfill the
resonance condition
h � V = Em+1 � Em
h: Planck�s constant.
This fact is the basis for electron spin resonance, in which the
resonance signal is detected using radio-frequency technology.
The electrons can often be regarded as free electrons. The g-factor
then deviates only slightly from that of the free electron (g =
2.0023), and the resonance frequency V in a magnetic field of
1 mT is about 78.0 MHz. The actual aim of electron spin resonance
is to investigate the internal magnetic fields of the sample
substance, which are generated by the magnetic moments of the
adjacent electrons and nuclei.
The first two experiments verify electron spin resonance in
diphenyl-picryl-hydrazyl (DPPH). DPPH is a radical, in which a
free electron is present in a nitrogen atom. In the simple configuration
of the first experiment, the magnetic field B which fulfills
the resonance condition is determined for three different resonance
frequencies V. In the second experiment, the resonance
frequencies can be set in a continuous range from 13 to 130
MHz. The aim of the evaluation in both cases is to determine the
g factor.
The object of the final experiment is to verify resonance absorption
using a passive oscillator circuit.