| 1. |
- Kondyurin, A.V., et al.
(författare)
-
Pulse and continuous ion beam treatment of polyethylene
- 2003
-
Ingår i: Vacuum. ; 68, s. 341-347
-
Tidskriftsartikel (refereegranskat)abstract
- Polyethylene (PE) films were treated by a nitrogen ion beam with an energy of 20 keV at a quasicontinuous regimewith low current density and at a pulse-periodical regime with high current density. IR ATR spectra and UV spectrashowed significant differences in structural changes of PE treated by pulse and continuous treatment at the sameaverage current density. The changes in the molecular structure that are induced by ion beams, i.e. the appearance ofaromatic cycles, unsaturated bonds and carbonyl groups in PE, have a similar qualitative character for all types of ionbeam regimes. However, the same degree of structural changes is achieved at lower dose in the pulse regime than in thecontinuous regime. At equal treatment parameters (ion energy, dose treatment, average current density) the pulseregime leads to a higher concentration of unsaturated and oxygen-containing groups then the continuous regime. Thiseffect at the pulse regime can be explained by the high current density in the single pulse, at which a high localtemperature is generated in the ion track field of the polymer. Probably this leads to a wave of internal stress, and theseeffects additionally stimulate structural changes in the polymer at pulsed ion beam treatment.
|
|
| 2. |
- Sandell, A, et al.
(författare)
-
Metalorganic Chemical Vapor Deposition of Anatase Titanium Dioxide on Si: Modifying the Interface by Pre-Oxidation.
- 2003
-
Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 530:1-2, s. 63-70
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of TiO2 films on clean and pre-oxidized Si(1 1 1) through chemical vapor deposition of titanium(IV) isopropoxide (TTIP) in ultra-high vacuum has been examined by synchrotron radiation photoelectron spectroscopy, X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy. In both cases, TTIP deposition at 500 °C eventually results in an anatase TiO2 film with a carbon-free surface and the surface morphology of the anatase films is very similar. By using a novel way of combining photoemission and XAS data, it is demonstrated that the two situations have substantially different interfacial properties. Pre-oxidation of the surface at 500 °C passivates the surface so that the thickness of the amorphous TiSixOy interface layer decreases from 30–35 to 15–25 Å and eliminates the formation of interfacial carbon completely.
|
|
| 3. |
- Andreoiu, Corina, et al.
(författare)
-
Doorway States in the Gamma Decay-out of the Yrast Superdeformed Band in 59Cu
- 2003
-
Ingår i: Physical Review Letters. - 1079-7114. ; 91:23
-
Tidskriftsartikel (refereegranskat)abstract
- The decay-out process of the yrast superdeformed band in Cu-59 has been investigated. The firm determination of spin, parity, excitation energy, and configuration of the states involved in this process constitutes a unique situation for a detailed understanding of the decay-out mechanism. A theoretical model is introduced that includes a residual interaction and tunneling matrix element between bands, calculated in the configuration-dependent cranked Nilsson-Strutinsky model. This interaction causes the decay to occur via a small number of observed doorway states.
|
|
| 4. |
- Cardona, R., et al.
(författare)
-
High-spin structure of normal-deformed bands in 84Zr
- 2003
-
Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 68, s. 1-024303
-
Tidskriftsartikel (refereegranskat)abstract
- The reaction 58Ni(32S, α2p) at E lab= 135 MeV was used to populate high-spin states in 84Zr. The complete GAMMASPHERE and MICROBALL arrays were used to obtain clean γ- γ- γ line shapes to be analyzed by the Doppler shift attenuation method and to determine 27 lifetimes in the ground-state band and in two excited bands. Side-feeding times were also measured by comparing the line shapes gated with transitions above and below the state under study. The deduced electric quadrupole moments for the ground-state band are consistent with a very slow reduction with frequency with values ranging between 2.4(3) and 2.0(1)e b. The negative-parity bands feature also an approximate constancy of quadrupole moment with values similar to those in the ground-state band. Cranking calculations agree with this behavior in both parity bands and suggest an interpretation of the upper states in the ground-state band as part of a very slowly terminating band. Shell-dependent cranked Nilsson calculations explain a fourth γ cascade as pertaining to a noncollective structure terminating at I = 20+.
|
|
| 5. |
- Hellborg, Ragnar, et al.
(författare)
-
Accelerator mass spectrometry - an overview
- 2003
-
Ingår i: Vacuum. - 0042-207X. ; 70:2-3, s. 365-372
-
Tidskriftsartikel (refereegranskat)abstract
- The technique of accelerator mass spectrometry (AMS) has spread worldwide since its first demonstration 25 years ago. The equipment used today is very diverse and dedicated accelerators as well as old "nuclear physics machines" can be found in the nearly 50 AMS laboratories today. The most widely spread application of AMS is for radiocarbon dating. However, AMS with C-14 as well as with other long-lived isotopes have also found applications in many other fields in physics and beyond.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Lundin, Magnus, et al.
(författare)
-
Compton scattering from the deuteron and extracted neutron polarizabilities
- 2003
-
Ingår i: Physical Review Letters. - 1079-7114. ; 90:19
-
Tidskriftsartikel (refereegranskat)abstract
- Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45degrees, 125degrees, and 135degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N) + beta(N) = 17.4 +/- 3.7 and alpha(N) - beta(N) = 6.4 +/- 2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p) - beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n) = 8.8 +/- 2.4(total) +/- 3.0(model) and beta(n) = 6.5 -/+ 2.4(total) -/+ 3.0(model), respectively.
|
|
| 9. |
- Park, HI, et al.
(författare)
-
Rotational structures near 40h in La-123
- 2003
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 68:4
-
Tidskriftsartikel (refereegranskat)abstract
- The neutron-deficient nucleus La-123 was studied via the Mo-92(Ca-40,2ap) reaction at a beam energy of 184 MeV. Previously known bands were extended to a much higher spin, and in two cases the structures are now observed near 40 (h) over bar. In addition, three new sequences were identified and linked into previously known bands. The lowest (pi,alpha)=(+,-1/2) structure displays characteristics similar to those of analogous bands in La-127,La-129, which have been proposed as examples of smooth band termination. Cranked Nilsson-Strutinsky calculations were compared with the experimental data in La-123 to determine whether this band is approaching a terminating state as well.
|
|
| 10. |
- Pavan, J, et al.
(författare)
-
Lifetime measurements and terminating structures in Nb-87
- 2003
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:3: 034316
-
Tidskriftsartikel (refereegranskat)abstract
- Two experiments have been performed using the Ni-58(S-32,3p) reaction at 135 MeV with Gammasphere and the Microball to study the high-spin structure of the transitional nucleus Nb-87. The first experiment using a thin target provided a considerable extension and refinement of the level scheme, as well as firm spin assignments from directional correlation of oriented nuclei. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of beta(2)similar to0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transitions between some pairs of bands. The experimental results were compared with calculations performed within the cranked Nilsson-Strutinsky approach. The calculations generally reproduce the irregularities in the structure of the yrast lines and plunging transition quadrupole moments Q(t) within the bands explaining them as reflections of configuration changes and an approach of band termination, respectively.
|
|
