2. Born May -- 25, 1865, Zonnemaire,
Neth.
Died Oct. 9, 1943, Amsterdam,
Dutch physicist who shared
with Hendrik A. Lorentz the Nobel
Prize for Physics in 1902 for his discovery
of the Zeeman effect
Zeeman, who had been a student of
Lorentz at the University of Leiden,
began lecturing at Leiden in 1890.
Pieter Zeeman
3. Six years later, at the suggestion of Lorentz, he investigated the
effect of magnetic fields on a source of light and found that each of the
lines in the spectrum of emitted light split into several lines; this
became known as the Zeeman effect.
The atomic energy levels, the transitions between these levels, and
the associated spectral lines discussed to this point have implicitly
assumed that there are no magnetic fields influencing the atom.
If there are magnetic fields present, the atomic energy levels are split
into a larger number of levels and the spectral lines are also split.
This splitting is called the Zeeman Effect.
Zeeman Effect
4. Observation along the magnetic field vector corresponds to the longitudinal
Zeeman effect and perpendicular to it to the transverse Zeeman effect, respectively.
The normal Zeeman effect is characterized by a triplet or doublet splitting of the
spectral line in case of transverse or longitudinal observation, respectively.
The middle line in the triplets represents the component of the spectral line
which is unaffected by the magnetic field, the other two lines shift by the same
amount to higher and lower wavelengths, respectively, due to the applied field.
Experimental Observation
5. Depending on the observation direction, the polarization of the split lines is
different.
In the longitudinal case, circular polarization occurs with opposite sense of
rotation for the two components.
Transversally, the middle component of the triplet is polarized parallel to the
field and the other two perpendicular. For the anomalous Zeeman effect, the
splitting is more complicated, even if the shift is still proportional and
symmetrical to the applied field.
Cont..,
6. Born April 15, 1874, Schickenhof, Ger.
died June 21, 1957, Traunstein, W. Ger.
German physicist who won the
1919 Nobel Prize for Physics for his
discovery in 1913.
Johannes Stark
7. An electric field would cause splitting of the lines in
the spectrum of light emitted by a luminous substance; the
phenomenon is called the Stark effect
Or
The Stark effect is the electric analogue to the Zeeman effect, i.e.,
a particle carrying an electric dipole moment, like the H-atom,
will get a splitting of its energy levels when subjected to an
exterior electric field.
As the splitting of a line of the helium spectrum shows, the
splitting is not symmetric like that of the Zeeman effect.
Stark Effect
8. The splitting of the energy levels by an electric field first requires
that the field polarizes the atom and then interacts with the resulting
electric dipole moment.
That dipole moment depends upon the magnitude of Mj, but not its
sign, so that the energy levels show splitting proportional to quantum
numbers J+1 or J+1/2, for integer and half-integer spins respectively.
Earlier experimenters had failed to maintain a strong electric field in
conventional spectroscopic light sources because of the high electrical
conductivity of luminous gases or vapours.
Stark observed the hydrogen spectrum emitted just behind the
perforated cathode in a positive-ray tube.
Stark Effect Experimental Study
9. With a second charged electrode parallel and close to this cathode, he
was able to produce a strong electric field in a space of a few millimetres.
At electric field intensities of 100,000 volts per centimetre, Stark observed
with a spectroscope that the characteristic spectral lines, called Balmer
lines, of hydrogen were split into a number of symmetrically spaced
components, some of which were linearly polarized (vibrating in one
plane) with the electric vector parallel to the lines of force, the remainder
being polarized perpendicular to the direction of the field except when
viewed along the field.
Cont..,
10. This transverse Stark effect resembles in some respects the transverse
Zeeman effect, but, because of its complexity, the Stark effect has relatively
less value in the analysis of complicated spectra or of atomic structure.
Historically, the satisfactory explanation of the Stark effect (1916) was one
of the great triumphs of early quantum mechanics.
Cont..,
