Total cross section of the 3 H ( p , n ) 3 He reaction from threshold to 4.5 MeV

We report new measurements of the total cross section for the {sup 3}H(p,n){sup 3}He reaction from threshold (E{sub p}=1.02 MeV) to E{sub p}=4.5 MeV. The experiment utilized specially prepared Ti-{sup 3}H targets, and neutrons were detected using a 4{pi} detector. A weak resonant structure due to an excited state in {sup 4}He is observed which was not seen in previous cross section measurements. A new expression for the {sup 3}He(n,p){sup 3}H thermonuclear reaction rate for temperatures below 10 GK is presented which will allow for more accurate calculations of the yields of light elements produced by big-bang nucleosynthesis. {copyright} {ital 1999} {ital The American Physical Society}