| Abstract |
This work presents a cavity-enhanced scheme for the measurement of the atomic iodine
spectrum, comprising a four-mirror bow-tie cavity, which increases the effective interaction
pathlength of iodine atoms with light, by a factor – essentially – equal to the average number
of intracavity photon round-trips.
It also doubles as the first steps towards a new type of atomic parity non-conservation (PNC)
experiment. In 1959, Zel’dovich first considered the possibility of measuring PNC in atomic
transitions, and suggested that if a parity violating weak neutral-current interaction between the
electron and the nucleus exists, then the interference with a parity conserving electromagnetic
interaction between the electron and the nucleus would make the atomic system optically
active. So, the ability to perform measurements of circular birefringence with high sensitivity
would constitute a way to measure PNC in a low-energy, atomic physics experiment.
The Standard Model, predicts a weak parity non-conserving transition amplitude E1PNC
between states of the same parity in certain atomic and molecular systems. Measurement of the
E1PNC transition amplitude is possible through the interference with the amplitude of a parity
allowed transition. In the vicinity of a parity-allowed magnetic-dipole M1 transition, the
interference M1-E1PNC leads to natural optical activity.
As a PNC candidate, iodine offers a number of advantages: a high atomic number, Z, which
enhances the PNC effect, a strong M1 transition with which the PNC amplitude can interfere,
readily available means to create significant atomic populations, even at room temperature, a
large number of isotopes, where combined measurements can eliminate deficiencies in our
theoretical understanding of atomic iodine, the ability to directly compare results with the bestto-date atomic PNC experiment, that on cesium performed by the C.E. Wieman group in the
late 1990s, and more. The main aim of this thesis is to study the iodine magnetic-dipole, M1,
transition 52P1/2 → 52P3/2 at 1315 nm, and to measure, for the first time, the electric quadrupole
E2 component between the same states, which is expected to provide unambiguous information
about a specific component of the PNC interaction, that owing to the elusive anapole moment
of the nucleus. The cavity enhancement outlined above is expected to allow for the study of
very small signals, such as PNC optical rotation.
As a further means of enhancement, we also study the effects of increased temperature for the
production of higher atomic iodine column densities, in order to maximize the PNC signal.
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Cavity-enhanced atomic Iodine spectroscopy: towards PNC optical rotation measurements
