Spectroscopy of [sub 199,201]At

The excited states of 199At and 201At were studied using fusion evaporation reactions, a gas-filled recoil separator and various tagging methods. The level scheme of 201At was extended a lot including a cascade of magnetic dipole transitions, that is suggested to form a shears band. In addition, a 29/2+ [T1/2 = 3.39(9) s] isomeric state was observed. The 29/2+ state is suggested to originate from the p(h9/2) j200Po; 11i configuration, and it depopulates through 269-keV E2 and 339-keV E3 transitions. In both nuclei 199,201At we have observed also the isomeric 1/2+ [T1/2 = 273(9), 45(3) ms, respectively] intruder state, that is suggested to originate from the p(s1/2)1 configuration. The 1/2+ state decays through 103- keV and 269-keV E3 transitions in 199,201At, respectively. In both nuclei the 1/2+ state is fed from 3/2+ and 5/2+ states, which are suggested to originate from the p(d3/2)1 and p(d5/2)1 configurations, respectively

Energeettisten protonien jarruuntuminen nestemäisessä vedessä

Tämän työn tarkoituksena oli mitata protonien jarruuntumiskyky nestemäisessä vedessä energia-alueella 4 - 20 MeV. Työssä käytettiin micro channel plate -pohjaisia lentoaikailmaisimia. Lopputulosten suhteelliset virheet vaihtelivat välillä 2,0 - 16,5 % mediaanin ollessa 4,2 % ja keskiarvon 5,3 %. Saadut tulokset olivat hyvässä sopusoinnussa ICRU:n raportin numero 49 antamien simuloitujen arvojen kanssa. Energialtaan 4 - 16 MeV protonien mitatut jarruuntumiskyvyt poikkesivat noin yhden prosentin tai vähemmän simuloiduista arvoista. Energia-alueella 16 - 20 MeV protonien mitatut jarruuntumiskyvyt olivat noin 4 - 8 % suuremmat kuin ICRU:n antamat simuloidut arvot. Mitattuja arvoja verrattiin myös SRIM-2008.04 -ohjelmalla simuloituihin arvoihin. Energialtaan 9 - 20 MeV protonien jarruuntumiskyvyt olivat sopusoinnussa SRIM:n antamien arvojen kanssa. Kuitenkin tätä pienemmillä energioilla SRIM:n simuloimat jarruuntumiskyvyt olivat noin 3 % suuremmat kuin mitatut arvot, ja nämä arvot eivät olleet sopusoinnussa mitattujen arvojen kanssa

Determination of absolute internal conversion coefficients using the SAGE spectrometer

A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.peerReviewe

Confirmation of the new isotope 178Pb

The extremely neutron-deficient isotope 178Pb has been produced. The GREAT spectrometer at the focal plane position of the gas-filled separator RITU was used to study the α decay of 178Pb and its α-decay chain through α-α correlations. The α decay was measured to have an energy and half-life of Eα= 7610(30) keV and t1/2 = 0.21+0.21 −0.08 ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and proximity potential model. The α-decay reduced width and hindrance factor for 178Pb were deduced and correspond to an unhindered l = 0 transition. In addition, the mass excess of 178Pb and the α-decay Q value were calculated from the experimental results and compared to theoretical values.peerReviewe

Decay spectroscopy of 179 82 Pb 97 and evidence for a 9/2− intruder state in 179 81 Tl 98

The very neutron-deficient isobars 179Pb and 179Tl have been produced using the fusion-evaporation reactions 104Pd(78Kr,xpyn), where x≤1 and y≥2. The gas-filled separator RITU was employed to transport and separate the recoiling nuclei of interest from the scattered beam and unwanted products. The GREAT spectrometer was used to study the decay properties through α−α and α−γ correlations, which has allowed the ground state of 179Pb to be assigned as Iπ=9/2−. The decay of 179Pb was measured to have an α-particle energy and half-life of Eα=7348(5)keV and t1/2=2.7(2) ms, respectively. A search for a νi13/2 state in 179Pb was performed, but only a limit of excitation energy and half-life was obtained. In 179Tl a t1/2=114+18−10 ns isomeric state, likely at an excitation energy of 904.5(9) keV, was identified and is tentatively assigned to be a 9/2− proton intruder state.peerReviewe

Experimental study of isomeric intruder ½+ states 197,203At

A newly observed isomeric intruder ½ + state [ T ½ = 3.5 ( 6 ) ms ] is identified in 203 At using a gas-filled recoil separator and fusion-evaporation reactions. The isomer is depopulated through a cascade of E 3 and mixed M 1 / E 2 transitions to the 9 / 2 − ground state, and it is suggested to originate from the π ( s ½ ) − 1 configuration. In addition, the structures above the ½ + state in 203 At and 197 At are studied using in-beam γ -ray spectroscopy, recoil-decay tagging, and recoil-isomer decay tagging methods. The ½ + state is fed from 3 / 2 + and 5 / 2 + states, and the origin of these states are discussed.peerReviewe

Detailed spectroscopy of 195Bi

An experiment focused on the study of shape coexistence and new high-spin structures in 195 Bi has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the 13 / 2 + isomeric state was extended up to I π = ( 49 / 2 + ) and an energy of 5706 keV. The I π = 31 / 2 + member of the π i 13 / 2 band was also found to feed a new long-lived isomeric state with an excitation energy of 2616 keV and a spin and parity of I π = 29 / 2 + . The half-life of the 29 / 2 + isomeric state was determined to be 1.49 ( 1 ) μ s . It decays via the emission of 457-keV E 2 and 236-keV E 1 transitions, respectively. A low-energy 46-keV E 2 transition has been identified to depopulate the ( 29 / 2 − ) isomeric state, with a measured half-life of T 1 / 2 = 614 ( 5 ) ns . This transition allows the excitation energy of the isomeric state to be determined as 2381 keV. The feeding patterns of both 29 / 2 + and ( 29 / 2 − ) isomeric states have also been described. This is the first time collective structures have also been observed up to high spins and excitation energies in the neutron-deficient 195 Bi nucleus. Evidence for the manifestation of shape coexistence in 195 Bi is also discussed.peerReviewe

Spin-dependent evolution of collectivity in 112Te

The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus 112Te has been studied by measuring the reduced transition probability of excited states in the yrast band. In particular, the lifetimes of the 4+ and 6+ excited states have been determined by using the recoil distance Doppler-shift method. The results are discussed using both large-scale shell-model and total Routhian surface calculations.peerReviewe

Lifetime measurement of the first excited 2+ state in 112Te

The lifetime of the 2+ → 0+ g.s. transition in the neutron-deficicient nucleus 112Te has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is B(E2 :0+ g.s. → 2+) = 0.46 ± 0.04 e2b2, indicating that there is no unexpected enhancement of the B(E2 :0+ g.s. → 2+) values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations.peerReviewe