  Short-lived radionuclides (SLRs) with lifetimes \tau < 100 Ma are known to
have been extant when the Solar System formed over 4.5 billion years ago.
Identifying the sources of SLRs is important for understanding the timescales
of Solar System formation and processes that occurred early in its history.
Extinct 36Cl (t_1/2 = 0.301 Ma) is thought to have been produced by interaction
of solar energetic particles (SEPs), emitted by the young Sun, with gas and
dust in the nascent Solar System. However, models that calculate SLR production
in the early Solar System (ESS) lack experimental data for the 36Cl production
reactions. We present here the first measurement of the cross section of one of
the main 36Cl production reactions, 33S(\alpha,p)36Cl, in the energy range 0.70
- 2.42 MeV/A. The cross section measurement was performed by bombarding a
target and collecting the recoiled 36Cl atoms produced in the reaction,
chemically processing the samples, and measuring the 36Cl/Cl ratio of the
activated samples with accelerator mass spectrometry (AMS). The experimental
results were found to be systematically higher than the cross sections used in
previous local irradiation models and other Hauser-Feshbach calculated
predictions. However, the effects of the experimentally measured cross sections
on the modeled production of 36Cl in the early Solar System were found to be
minimal. Reactions channels involving S targets dominate 36Cl production, but
the astrophysical event parameters can dramatically change each reactions'
relative contribution.
