Directory: levels/ File: levels.readme (September 20, 2002) ********************************************* levels/zxxx.dat Processed discrete level schemes from ENSDF-II (provided by T. Belgya on September 20, 2002) ********************************************** Content ------- Discrete level schemes processed and arranged in a way suitable for nuclear reaction calculations. ENSDF of 1998 has been used as a main source of data. The library contains 2546 nuclear level schemes, with at least 1 known level, within mass range A=1-266 and Z=0-109. The basic set includes 113346 levels (out of which 8554 have unknown level energies denoted with +X or +Y) and 159323 gamma-transitions. The total number of levels with unique spin is 12956, and there are additional 8708 levels with uncertain spin or parity assignment. For the purpose of reaction calculations the library was completed by estimating data missing in the basic ENSDF set: - unique spins and parities for all levels below the cutoff energy Umax were generated by (i) analyzing gamma-transitions (3560), (ii) drawing from the assumed spin distribution (3551), and (iii) selecting from the list suggested in ENSDF (6280). - 21595 Internal Conversion Coefficients (ICC) for electromagnetic transitions available in the original ENSDF data set were supplemented with 92634 ICCs calculated by cubic spline interpolation of values tabulated by Hager and Seltzer for the K, L, and M shells and by Dragoun, Plajner, and Schmetzler for the N+O+... shells. - if ENSDF reported de-exciting transitions from a level but did not specify the decay modes, 100% electromagnetic decay was assigned to the level. If other decay modes were indicated, the percentage of the electromagnetic mode was obtained from the available information on the decay modes and flagged by %IT or %G in the data files. - if ENSDF reported one and only one transition from a given level and branching ratio for this transition was 0 a value of 1 (100%) was assigned. The level schemes were analyzed using constant temperature fits to the cumulative plots for all nuclei with at least 30 known levels in order to determine the cut-off energy (Umax) and the corresponding cumulative number of levels (Nmax) up to which schemes can be assumed complete and suitable for reaction calculations. These results were extended to cover all remaining nuclei using the nuclear temperature inferred from the above analysis. The energy Uc, corresponding to the highest level with known and unique spin and parity assignment in the ENSDF, was subsequently determined for all nuclei. For more details, user is referred to the RIPL-2 TECDOC and levels-readme.html file. WARNING!!! ---------- These data are intended ONLY for nuclear reaction calculations and NOT for nuclear structure studies. This warning refers particularly to inferred spins and related quantities such as ICCs. Format ------ Data are stored in 110 files, each of them containing full isotopic chain of a given element. File names indicate an element by referring to its atomic number (e.g., z026.dat). The format consists of three types of records: (i) identification, (ii) level, and (iii) gamma. Each isotope begins with an identification record such as the one shown below for the case of Mg-22 (heading has been introduced to facilitate reading but does not show up in the actual file): SYMB A Z Nol Nog Nmax Nc Sn[MeV] Sp[MeV] 22Mg 22 12 17 18 9 4 19.382000 5.497000 SYMB : mass number with symbol of the element A : mass number Z : atomic number Nol : number of levels in the decay scheme Nog : number of gamma rays in the decay scheme Nmax : maximum number of levels up to which the level scheme is complete Nc : number of a level up to which spins and parities are unique Sn : neutron separation energy in MeV Sp : proton separation energy in MeV The corresponding FORTRAN format is (a5,6i5,2f12.6) The identification record is followed by the level record, which in turn is followed by the pertinent gamma records if decay of the level is known. This combination is repeated for all levels in a given isotope. An example below shows level records for the ground state and the first excited state in Mg-22: N1 Elv[MeV] s p T1/2 Ng J unc spins nd m percent mode 1 0.000000 0.0 1 3.86E+00 0 0+ 1 = 100.0000 %EC+%B+ 2 1.246300 2.0 1 2.10E12 1 2+ 0 Each level record may contain the following quantities: Nl : sequential number of a level Elv : energy of the level in MeV s : level spin (unique). Whenever possible unknown spins up to Umax were inferred. Unknown and undetermined spins are entered as -1.0 p : parity (unique). If the parity of the level was unknown, positive or negative was chosen with equal probability. Parities were determined up to Umax as in the case of spins. The method of choice is not coded. T1/2 : half-life of the level (if known). All known half-lives or level widths were converted into seconds. Half-lives of stable nuclei are represented as -1.0E+0. Ng : number of gamma rays de-exciting the level. J : flag for spin estimation method. unc : flag for an uncertain level energy. When impossible to determine, the relative energy of the band, the energy of these band heads were set to 0.0 keV or, if the level order is known, to the preceding level energy with a note that an unknown energy X should be added. The notation uses X+, Y+, Z+ etc. for different bands. spins : original spins from the ENSDF file. nd : number of decay modes of the level (if known). Values from 0 through 10 are possible; 0 means that the level may decay via gamma-emission, and other decay modes are not known. m : decay percentage modifier; informs a user about major uncertainties. The modifiers are copied out of ENSDF with no modification, and can have the following values: =, <, >, ? (unknown, but expected), AP (approximate), GE (greater or equal), LE (less or equal), LT (less then), SY (value from systematics). percent: percentage decay of different decay modes. As a general rule the various decay modes add up 100%. There are, however, two exceptions: (i) when a small percentage decay is present, the sum may be slightly more then 100% due to rounding error, (ii) when beta -decay is followed by a heavier particle emission, the percentage of the beta-delayed particle emission is given as a portion of the beta-decay and the sum can be substantially larger then 100%. Naturally, when the modifier is "?" the sum is indefinite. mode : short indication of decay modes of a level (see Table below). The corresponding FORTRAN format is (i3,1x,f10.6,1x,f5.1,i3,1x,(e10.2),i3,1x,a1,1x,a4,1x,a18,i3,10(1x,a2,1x,f10.4,1x,a7)) Two typical examples of the gamma records are given below (Nb-94): Nf Eg[MeV] Pg Pe ICC 3 0.055 4.267E02 1.301E01 2.050E+00 1 0.113 7.499E01 8.699E01 8.699E01 Nf : sequential number of the final state Eg : gamma-ray energy in MeV Pg : Probability that a level decays through the given gamma-ray emission. Pg is the ratio of the total electromagnetic decay of the level to the intensity of the gamma-ray. If no branching ratio is given in the ENSDF file, Pg=0. Pe : Probability that a level decays with the given electromagnetic transition, i.e., ratio of the total electromagnetic decay of the level to the intensity of the given electromagnetic transition. The sum of electromagnetic decays is normalized to 1. If no branching ratio is given in the ENSDF file, Pe=0. ICC : Internal conversion coefficient of a transition. The corresponding FORTRAN format is (39x,i4,1x,f10.3,3(1x,e10.3)) Coding of decay modes. Some minor possibilities, such as decay through the emission of Ne-20, are neglected. ----------------------------------------------------- Code Meaning ----------------------------------------------------- %B beta- decay %EC electron capture %EC+%B+ electron capture and beta+ decay %N neutron decay %A alpha decay %IT isomeric transition %P proton decay %3HE He-3 decay %B+P beta+ delayed proton decay %BN beta- delayed neutron decay %SF spontaneous fission %ECP electron capture delayed proton decay %ECA electron capture delayed alpha decay %G gamma decay %B2N beta- delayed double neutron decay %B+2P beta+ delayed double proton decay ------------------------------------------------------ The FORTRAN90 code (levels-read.f90) that reads the library is provided in the archive levels-fortran.tgz.