Abstract. The cross sections for the Na.4D/! Na.4F / excitation energy transfer induced by collisions with He, Ar and Na ground-state atoms have been measured. The sodium atoms in the 4D state have been produced by two-photon excitation using cw laser radiation at 578.89 nm. Within a model which takes into account collisional population and depopulation of the 4F level as well as radiative relaxation (direct or cascade) of the 3D, 4P, 4D and 4F states ending in the 3P level, the rate for the Na.4D / ! Na.4F / collisional transfer turns out to be related to the ratio of the steady-state populations created in 3D and 4D states. They have been determined by measuring the fluorescence intensities of the 3D! 3P and 4D! 3P transitions. The measurements yield the following cross section values for those
Cross sections for the collisional
l mixing of
Na(n2D) states from
n=5to14 by
N2 and CO have been measured by time-resolved laser fluorescence and calculated in a two-state approximation by assuming the perturbing gases are spherically symmetric. For both CO and
N2 the experimental cross sections rise sharply from
n=5 to
n=10 and remain constant for
n>10. The theoretical calculations overestimate the experimental cross sections by a factor of 3 from
n=10to12, but are in good agreement for the smaller
n values.
We report high-resolution measurements of the differential cross section for scattering Na in its
3S21 and
3P23 states from Ne. A new scheme is used to maintain a high fraction (\ensuremath{\sim}20%) of an atomic beam of Na in the excited state for many radiative lifetimes using a single-mode cw dye laser. The differential cross sections are interpreted to yield interatomic potential curves for both the $X\ensuremath{\Sigma}$ and $A\ensuremath{\Pi}$ states of the NaNe molecule which seriously disagree with recent pseudopotential calculations.
Differential scattering of Na 3S
sub1/
sub2 and 3P
sub3/
sub2 from Ne: Determination of ground- and excited-state potentials for NaNe
We report high-resolution measurements of the differential cross section for scattering Na in its 3S
sub1/
sub2 and 3P
sub3/
sub2 states from Ne. A new scheme is used to maintain a high fraction (approx.20%) of an atomic beam of Na in the excited state for many radiative lifetimes using a single-mode cw dye laser. The differential cross sections are interpreted to yield interatomic potential curves for both the X
Sigma and APi states of the NaNe molecule which seriously disagree with recent pseudopotential calculations. (AIP)
In Na, the energy gap $\ensuremath{\Delta}E$ between the
n,
d state and the
n,
l>2 states is ten times larger than $\ensuremath{\Delta}E$ between
n,
f and the
n,
l>3 states. To investigate the effect of this difference on the
d- and
f-state
l-mixing cross sections, ${\ensuremath{\sigma}}_{d}$ and ${\ensuremath{\sigma}}_{f}$, we have recently carried out experiments to measure ${\ensuremath{\sigma}}_{d\ensuremath{-}f}$, the
l-mixing cross sections for a microwave-induced mixture of
d and
f states. Using the previously measured values of ${\ensuremath{\sigma}}_{d}$, we have derived values of ${\ensuremath{\sigma}}_{f}$ which have the same
n dependence as ${\ensuremath{\sigma}}_{d}$. ${\ensuremath{\sigma}}_{f}$ is larger than ${\ensuremath{\sigma}}_{d}$ for Ne, but smaller for He and Ar. In addition, we have analyzed the final states after one collision with Ar using selective field ionization of the
17l states and have observed that after one collision all the
l states are equally populated indicating that there are no $\ensuremath{\Delta}l$ selection rules for the process. This confirms the earlier suggestion that
l mixing is caused by a short-range interaction.
The cross sections for the excitation energy transfer induced by collisions with He, Ar and Na ground-state atoms have been measured. The sodium atoms in the 4D state have been produced by two-photon excitation using cw laser radiation at 578.89 nm. Within a model which takes into account collisional population and depopulation of the 4F level as well as radiative relaxation (direct or cascade) of the 3D, 4P, 4D and 4F states ending in the 3P level, the rate for the collisional transfer turns out to be related to the ratio of the steady-state populations created in 3D and 4D states. They have been determined by measuring the fluorescence intensities of the and transitions. The measurements yield the following cross section values for those processes investigated: , and , at .