Directory: fission/ File: fis-barrier-liquiddrop.readme (April 30, 2002) ********************************************************* fis-barrier-liquiddrop.for Subroutine BARFIT for fission barrier calculations (provided by A. V. Ignatyuk on April 30, 2002) *************************************************** MACROSCOPIC MODEL OF ROTATING NUCLEI A.Sierk Los Alamos National Laboratory (USA) Content ------- Subroutine BARFIT was written by A. Sierk for calculation of fission barriers in the framework of the liquid drop model [1]. To obtain the barrier hight relative to the ground state the corresponding shell correction should be added to the calculated liquid-drop barrier. Reproduced below is the comment part of the barfit.f code: This subroutine returns the barrier height bfis, the ground-state energy segs, in MeV, and the angular momentum at which the fission barrier disappears, eLmax, in units of h-bar, when called with integer arguments iz, the atomic number, ia, the atomic mass number, and il, the angular momentum in units of h-bar, (Planck's constant divided by 2*pi). The calculated barriers from which the fits were made were calculated in 1983-1985 by A. J. Sierk of Los Alamos National Laboratory Group T-9, using Yukawa-plus-exponential double folded nuclear energy, exact Coulomb diffuseness corrections, and diffuse-matter moments of inertia. The parameters of the model are those derived by Moller and Nix in 1979: r-0 = 1.16 fm, as = 21.13 MeV, kappa-s = 2.3 a = 0.68 fm. The diffuseness of the matter and charge distributions used corresponds to a surface diffuseness parameter (defined by Myers) of 0.99 fm. The calculated barriers for L = 0 are accurate to a little less than 0.1 MeV; the output from this subroutine is a little less accurate. Worst errors may be as large as 0.5 MeV; characteristic uncertainty is in the range of 0.1-0.2 MeV. The values of egs are generally approximated to within about 0.1-0.2 MeV; the largest deviation is about 0.5 MeV, near L-I for light nuclei. The fission barrier for il = 0 is calculated from a 7th order fit in two variables to 638 calculated fission barriers for z values from 20 to 110. These 638 barriers are fit with an rms deviation of 0.10 MeV by this 49-parameter function. If barfit is called with (iz,ia) values outside the range of the fit the barrier height is set to 0.0, and a message is printed on the default output file. For il values not equal to zero, the values of L at which the barrier is 80% and 20% of the L=0 value are respectively fit to 20-parameter functions of Z and A, over a more restricted range of A values, than is the case for L = 0. The value of L where the barrier disappears, Lmax, for 61 nuclei, is fit to a 35-parameter function of Z and A, with the same range of Z and A values as l-80 and l-20. Once again, if an (iz,ia) pair is outside of the range of validity of the fit, the barrier value is set to 0.0 and a message is printed. These three values (Bfis(L=0),L-80, and L-20) and the constraints of Bfis = 0 and d(Bfis)/dL = 0 at L = Lmax and L = 0 lead to a fifth-order fit to Bfis(L) for L> L-20. The first three constraints lead to a third-order fit for the region L < L-20. Format ------ Plain ACSII file with the FORTRAN source. References ---------- [1] A. Sierk, Phys. Rev. C33 (1986) 2039.