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

data to assumed matrix elements and in some cases have proven to be incorrect. A model-independentanalysis of multiple Coulomb excitation data, using the formalism employed by COULEX, is not practicaltaking into consideration the numerical effort necessary for such a task using even the capability of thenewest generation computers. To overcome this problem it is necessary to construct simple approximationsto the Coulomb excitation formalism, accurate enough to determine a search strategy in a multidimensionalspace of the matrix elements parametrizing both excitation and decay processes. The development of suchan approximation became the basis of the Rochester Coulomb excitation data analysis least-squares searchprogram, GOSIA, presented in this report. GOSIA was developed at the Nuclear Structure Research Laboratoryof the University of Rochester during 1980[CZO83] and was subsequently expanded and improved onthe basis of experience gained by the Rochester-Warsaw-Uppsala based Coulomb excitation collaboration.GOSIA is an experiment-oriented program. Although providing the possibility of running theoreticalcalculations (i.e. evaluation of excitation amplitudes and γ-decay yields for a given set of the matrix elements)it is primarily designed to perform a fit of the matrix elements to reproduce the large amount of experimentaldata. These data not only include the deexcitation γ-yields observed in a number of independent Coulombexcitation experiments, but also available spectroscopic information, such as branching ratios, E2/M1 mixingratios, nuclear level lifetimes and previously measured E2 matrix elements. All this information combinedallow determination of the full set of matrix elements for an investigated nucleus together with a realisticestimate of the errors of the fitted matrix elements. Finally, using the associated quadrupole rotationalinvariants code, SIGMA, it is possible, on a basis of the results obtained with GOSIA, to evaluate, ina model-independent way[CLI72, CLI86] the expectation values and the statistical distribution of the E2moments in the intrinsic frame, providing a clear insight into the collective properties of the nuclear states.Advances in heavy-ion accelerator facilities coupled with significantly more powerful γ-ray and heavy-iondetector systems has led to a significant increase in the size and complexity of the nuclear systems beingstudied. Fortunately, this growth in difficulty has been matched by a comparable advance in computertechnology allowing the code GOSIA to handle the increasingly more complicated systems being analyzedsince its inception in 1980.The code GOSIA is available free for use by anyone. However, all users must reference GOSIA[CZO83]in publications based on use of this code. Changes in the author list and/or in the name of the code arepossible only with the written approval of the authors. Errors and modifications should be communicated tothe authors. The code has been used extensively since 1980 and appears to be trouble free. Since the codeGOSIA is complicated, with extensively overlaid coding, users are strongly recommended to seek advicebefore attempting to make modifications. The goal is to maintain one freely available current version ofGOSIA for all users in order to minimize introducing errors in the code.1.2 A brief history of Gosia1965 - 1979:The genesis of Gosia dates back to 1965 when multiple Coulomb excitation work blossomed due to theadvent of heavy-ion accelerators, and the high-resolution Ge γ-ray detector, coupled with development in 1965of the Winther-de Boer semiclassical Coulomb excitation code COULEX [WIN65]. Between 1966 and 1978,Cline and coworkers used heavy-ion beams from the newly commissioned Rochester MP tandem acceleratorfacility plus the code COULEX to measure static quadrupole moments of the first excited 2 + states viaCoulomb excitation [CLI69a, LES70, GER70a, GER70b, LES72, TOW72, CLI73, TOW73, TOW75] Thiswork employed the particle γ-ray coincidence technique which necessited the development at Rochester of theγ-ray deexcitation code CEGRY[CLI74] that used the statistical tensors calculated by COULEX to predictthe subsequent γ-ray decay properties.Much higher Z beams became available with the commissioning of the SuperHILAC at Berkeley in 1975,and the UNILAC at GSI in 1976 which greatly advanced the field of multiple Coulomb excitation. Starting in1975 Cline, plus coworkers at Rochester, became heavily involved in studies of multiple Coulomb excitationusing heavy-ion beams from the SuperHILAC and the Rochester MP tandem. This work involved closecollaboration with the Diamond-Stephens group at Berkeley plus Rochester graduate students Ching-YenWu (1977-83) and Tomasz Czosnyka (1979-1982, 1984-87). In addition Julian Srebrny (1978) from Warsawand Lennart Hasselgren (1979-80) from Uppsala each spent a year in Rochester working on this researchprogram. This group, plus other collaborators, were involved in multiple Coulomb excitation studies of7