LEGENDRE EXPANSION OF THE NU(NU)OVER-BAR-REVERSIBLE-ARROW-E(-) KERNEL- INFLUENCE OF HIGH-ORDER TERMS()E()

We calculate the Legendre expansion of the rate of the process nu + <( nu)over bar> <----> e(+) + e(-) up to 3(rd) order estending previous r esults of other authors which only consider the 0(th) and 1(st) order terms. Using different closure relations for the moment equations of t he radiative transfer equation we discuss the physical implications of taking into account quadratic and cubic terms on the energy depositio n outside the neutrinosphere in a simplified model. The main conclusio n is that 2(nd) order is necessary in the semi-transparent region and gives good results if an appropriate closure relation is used.