coulomb excitation data analysis codes; gosia 2007 - Physics and ...

5.30 OP,YIEL (YIELDS)This option is mandatory if it is desired to calculate the yields of deexcitation γ-rays following Coulombexcitation. The first part of this option is used to input the internal conversion coefficients and the descriptionof the γ-ray detectors. This first section is used in conjunction with either OP,COUL or OP,GOSI. The secondpart of this option is used in conjunction with OP,GOSI to input additional information required for theleast-squares fitting such as normalization constants, γ-ray branching ratios, lifetimes, E2/M 1 mixing ratios,and diagonal or transitional E2 matrix element data to be included in the fit. The input to OP,YIEL mustbe complete and consistent with the option of the code selected. Section 7.4 shows the correct position ofOP,YIEL in the input stream for various calculations.OP,YIEL defines the “logical“ γ detectors, which are referred to everywhere in the input except inOP,GDET. Different logical detectors may be in fact the same “physical“ ones. This distinction allows toreduce the number of experiments defined in all cases where the setup used is symmetric with respect tothe beam axis. As an example, let us consider the experiment in which two particle detectors are placedsymmetrically about the beam axis at angles (θ, φ) and(θ, φ, +π), respectively. Gamma rays are detectedin coincidence with scattered particles in one Ge detector placed at position (θ g ,φ g ), so the scan of eventby-eventdata yields two γ spectra. A straightforward approach is to define two experiments, differing onlyby the placement of the Ge detector with respect to the scattered particles. Instead, one can define onlyone experiment (keeping in mind that the Coulomb excitation depends on θ, but not on φ) and two logicaldetectors, one at (θ g ,φ g ), and another at (θ g ,φ g +π). Both are identified as the same “physical“ detector, butdifferent sets of γ yields (both spectra resulting from the scan) are assigned to them. Such a manipulationsaves almost 50% of CPU time since evaluation of deexcitation γ yields requires negligible computation timecompared to the excitation calculation.GOSIA allows also to define logical detector clusters (see OP,RAW-5.20), i.e. sets of γ yields which resultfrom summing the raw spectra, therefore the number of experimental data sets is not always equal to thenumber of logical detectors. Further description will refer to the “logical“ detectors simply as γ detectors,which should be distinguished from either “physical“ detectors or data sets.Brief resumé of the input to OP,YIEL:OP, YIELIFLAG Assumes the values of 0 or 1. IFLAG =1means that the correction to the angular distributionof the γ-rays due to a finite distance traveled by the decaying nucleus will be included in the calculation(see Section 4.3). IFLAG =0switches off this correction.N1, N2 Number of energies (N1 ≤ 50) and multipolarities (N2) todefine the internal conversion coefficients.E 1 , E 2 , ..., E N1 Energy meshpoints for the internal conversion coefficients (in MeV), common for allmultipolarities for the nucleus of interest. The code uses four point interpolation between meshpoints.Note that the large discontinuities in the internal conversion coefficients at the K and L edges can betaken into account correctly by ensuring that there are at least two mesh points between the transitionenergy of interest and the nearest discontinuity; that is, so that the four point interpolation does notdoes straddle any discontinuity.I1 Multipolarity I1.CC(I1, 1)..CC(I1, N1) Internal conversion coefficients for multipolarity I1 at each energy meshpoint(N1 entries). Note that internal conversion coefficients can be obtained from the NNDC (US NationalNuclear Data center) at http://www.nndc.bnl.gov/bricc/.I2This sequence should be repeated for all multipolarities defined, i.e. N2 times.CC(I2, 1)..CC(I2, N1)NANG(I)..NANG(NEXP) Number of γ-ray detectors for each of the NEXP experiments. NANG(I)can be entered as its true value with a negative sign, which means that the γ detector setup is identical110