https://doi.org/10.1007/s100530170021
Measurement of the rotational alignment in the presence of the second order AC Stark effect
Physikalisches Institut, Westfälische Wilhelms-Universität Münster,
Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
Corresponding author: a hzach@nwz.uni-muenster.de
Received:
1
August
2000
Revised:
2
May
2001
Published online: 15 November 2001
The determination of the rotational quadrupole alignment of diatomic molecules via REMPI detection is
investigated. In this process a high focal intensity usually increases the detection probability. At high
intensities the AC Stark effect may cause a splitting of the normally degenerate mJ sublevels of a
rotational state J beyond the spectral width of the exciting radiation. This leads to a selective detection
of only certain mJ states with the consequence that deduced alignment factors can be misleading. From the
theoretical considerations line profiles are explicitly calculated for dynamic polarizabilities which
represent the 
transition of H2, in order to fit
an experimental (3{+}1) REMPI spectrum and to predict (1{+}1') line shapes as a function of laser intensity. It
is further shown that the deduced quadrupole alignment factor
is significantly changed by the
second order AC Stark effect when the intensities are chosen high enough to observe asymmetric broadened line
profiles. Different combinations of relative linear polarizations of the exciting and ionizing laser beams
are discussed.
PACS: 42.62.Fi – Laser spectroscopy / 33.55.Be – Zeeman and Stark effects / 33.15.-e – Properties of molecules
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001
