Symmetry energy and the isospin dependent equation of state

The isoscaling parameter $\alpha$, from the fragments produced in the multifragmentation of $^{58}$Ni + $^{58}$Ni, $^{58}$Fe + $^{58}$Ni and $^{58}$Fe + $^{58}$Fe reactions at 30, 40 and 47 MeV/nucleon, was compared with that predicted by the antisymmetrized molecular dynamic (AMD) calculation based on two different nucleon-nucleon effective forces, namely the Gogny and Gogny-AS interaction. The results show that the data agrees better with the choice of Gogny-AS effective interaction, resulting in a symmetry energy of $\sim$ 18-20 MeV. The observed value indicate that the fragments are formed at a reduced density of $\sim$ 0.08 fm$^{-3}$.Comment: 5 pages, 5 figures, Accepted for publication in Phys. Rev. C (Rapid Communication

Symmetry energy and the isoscaling properties of the fragments produced in 40^{40}Ar, 40^{40}Ca + 58^{58}Fe, 58^{58}Ni reactions at 25 −- 53 MeV/nucleon

The symmetry energy and the isoscaling properties of the fragments produced in the multifragmentation of $^{40}$Ar, $^{40}$Ca + $^{58}$Fe, $^{58}$Ni reactions at 25 - 53 MeV/nucleon were investigated within the framework of statistical multifragmentation model. The isoscaling parameters $\alpha$, from the primary (hot) and secondary (cold) fragment yield distributions, were studied as a function of excitation energy, isospin (neutron-to-proton asymmetry) and fragment symmetry energy. It is observed that the isoscaling parameter $\alpha$ decreases with increasing excitation energy and decreasing symmetry energy. The parameter $\alpha$ is also observed to increase with increasing difference in the isospin of the fragmenting system. The sequential decay of the primary fragments into secondary fragments, when studied as a function of excitation energy and isospin of the fragmenting system, show very little influence on the isoscaling parameter. The symmetry energy however, has a strong influence on the isospin properties of the hot fragments. The experimentally observed scaling parameters can be explained by symmetry energy that is significantly lower than that for the ground state nuclei near saturation density. The results indicate that the properties of hot nuclei at excitation energies, densities and isospin away from the normal ground state nuclei could be significantly different.Comment: 14 pages, 15 figure

Neutron to proton ratios of quasiprojectile and midrapidity emission in the 64^{64}Zn + 64^{64}Zn reaction at 45 MeV/nucleon

Simultaneous measurement of both neutrons and charged particles emitted in the reaction $^{64}$Zn + $^{64}$Zn at 45 MeV/nucleon allows comparison of the neutron to proton ratio at midrapidity with that at projectile rapidity. The evolution of N/Z in both rapidity regimes with increasing centrality is examined. For the completely re-constructed midrapidity material one finds that the neutron-to-proton ratio is above that of the overall $^{64}$Zn + $^{64}$Zn system. In contrast, the re-constructed ratio for the quasiprojectile is below that of the overall system. This difference provides the most complete evidence to date of neutron enrichment of midrapidity nuclear matter at the expense of the quasiprojectile

Moldless printing of silicone lenses with embedded nanostructured optical filters

In this work, both light-shaping and image magnification features are integrated into a single lens element using a moldless procedure that takes advantage of the physical and optical properties of mesoporous silicon (PSi) photonic crystal nanostructures. Casting of a liquid poly(dimethylsiloxane) pre-polymer solution onto a PSi film generates a droplet with a contact angle that is readily controlled by the silicon nanostructure, and adhesion of the cured polymer to the PSi photonic crystal allows preparation of lightweight (10 mg) freestanding lenses (4.7 mm focal length) with an embedded optical component (e.g., optical rugate filter, resonant cavity, and distributed Bragg reflector). The fabrication process shows excellent reliability (yield 95%) and low cost and the lens is expected to have implications in a wide range of applications. As a proof-of-concept, using a single monolithic lens/filter element it is demonstrated: fluorescence imaging of isolated human cancer cells with rejection of the blue excitation light, through a lens that is self-adhered to a commercial smartphone; shaping of the emission spectrum of a white light emitting diode to tune the color from red through blue; and selection of a narrow wavelength band (bandwidth 5 nm) from a fluorescent molecular probe

Photonically Encoded Silicone Lenses For Smartphone-Based Microscopy And Imaging In Biology And Nanomedicine

In this work [1], we describe the moldless preparation of a poly(dimethylsiloxane) (PDMS) lens embedding nanostructured porous silicon (PSi) optical components. Casting of uncured PDMS onto a PSi surface shapes a droplet with contact angle easily controllable by tuning of the nanostructure features (i.e., thickness and porosity of PSi). Design of the PSi layer as an optical component (e.g., distributed Bragg reflector, rugate filter, resonant cavity) allows the preparation of lightweight, freestanding PDMS lenses (10 mg mass and 4.7 mm focal length) with embedded optical elements. The fabrication process of the PDMS lens shows high reliability (yield >95%), low-cost (0.01 $), and good flexibility for a wide range of applications. For instance, using a single monolithic lens/filter element self-adhered to a commercial smartphone camera, we demonstrate: the fluorescence imaging and counting of live/dead isolated human cancer cells with high magnification and rejection of the excitation light; the selection of a narrow wavelength band from a fluorescent emission; and the tuning of the color of a white light emitting diode (from red to blue) through shaping of the emission spectrum

Resolving multiple particles in a highly segmented silicon array

The design, construction, and performance of a new highly segmented charged particle detector array, FIRST, are described. This forward angle annular array (2°≤θlab≤28°) has been developed to study peripheral and mid-central heavy-ion collisions at intermediate energies (E/A≈50MeV). FIRST consists of three individual telescopes that each utilize ion-passivated silicon detectors in either a Si(IP)-Si(IP)-CsI(Tl) stack or a Si(IP)-CsI(Tl) stack. This array provides elemental identification for 1≤Z≤50 with isotopic identification of lighter elements, Z≤13, over a wide dynamic range in energy. The high segmentation of each silicon detector provides good angular resolution in a compact geometry and allows deconvolution of multiple particles incident on a single telescope. The performance of the array in a commissioning experiment Zn64+Zn64,Bi209 at E/A=45MeV is shown. © 2005 Elsevier B.V