Giant resonances in (116)Sn from 240 MeV (6)Li scattering

Journals published by the American Physical Society can be found at http://publish.aps.org/Giant resonances in (116)Sn were measured by inelastic scattering of (6)Li ions at E(6)Li=240 MeV over the angle range 0(degrees)-6(degrees). Isoscalar E0-E3 strength distributions were obtained with a double folding model analysis. A total of 106(-11)(+27)% of the E0 EWSR was found in the excitation energy range from 8 MeV to 30 MeV with a centroid (m(1)/m(0)) energy 15.39(-0.20)(+0.35) MeV in agreement with results obtained with alpha inelastic scattering

A Novel Laboratory Course on Advanced Chemical Engineering Experiments

The chemical engineering curriculum in the United States has trained generations of technical experts who have successfully optimized chemical processes and products once they entered the chemical industry. The U.S. chemical industry, however, has entered a critical stage in which it must be able to create new and differentiated value through technical innovations that arc essential for long-term survival. This innovation process will require new skills that go far beyond the traditional expertise for the optimization of tasks possessed by young chemical engineers. The innovators must be able to identify new opportunities, explore the boundaries of technology, evaluate critical issues, develop and implement technologies, and communicate effectively with scientists and engineers from other disciplines. Therefore, one of the most important educational tasks of a modern university, in combination with a strong theoretical foundation, is to challenge students in laboratory courses to think, explore, hypothesize, plan, solve, and evaluate. The typical sequence of laboratory skills development stops short of introducing young engineers to the most critical aspects of experimental work. Chemical engineers usually begin developing their laboratory skills in chemistry courses, where experiments are closely managed. At this early stage in their development, students follow detailed instructions and learn basic principles by observing the results. In the undergraduate engineering laboratory course (the unit operations lab ), students have more freedom in experimental design but still have well-defined objectives and manipulate equipment someone else has set up. It is rare, however, for undergraduate students to be taught how to create new experiments. It is also rare for undergraduate students, and hence beginning graduate students, to have an appreciation for the care, planning, design, and testing required to produce equipment that will give reliable and useful results. Even such simple issues as leak testing or adapting analytical devices to new tasks are outside most students* experience. Even more important is an absence of opportunities to learn how the lessons learned from the failure of an approach can be fed back into the empirical process to seed the finally successful idea. All these skills require more creative freedom than is usually allowed in a well-structured laboratory course. In the novel laboratory teaching approach described here, we try to provide students with a learning environment that allows them to develop advanced experimental skills that are necessary for success in research and development environments

Elastic and inelastic scattering of 240-MeV (6)Li ions from (40)Ca and (48)Ca and tests of a systematic optical potential

Journals published by the American Physical Society can be found at http://publish.aps.org/Elastic and inelastic scattering of 240-MeV (6)Li particles from (40)Ca and (48)Ca were measured with the multipole-dipole-multipole spectrometer from 4 degrees <= theta(c.m.) <= 40 degrees. Optical potential parameters were obtained by fitting the elastic-scattering data with the double-folding model using the density-dependent M3Y NN effective interaction and B(E2) and B(E3) values obtained for low-lying 2(+) and 3(-) states agreed with the adopted values. The results are compared with those obtained using potentials derived from the systematics of potentials previously obtained for (24)Mg, (28)Si, (58)Ni, and (90)Zr. Cross sections for excitation of giant resonances were also calculated with the potentials obtained

Isoscalar giant resonance strength in (24)Mg

Journals published by the American Physical Society can be found at http://publish.aps.org/The giant resonance region from 9 MeV < E(x)< 60 MeV in (24)Mg has been studied with inelastic scattering of 240-MeV alpha particles at small angles, including 0(degrees). Isoscalar E0, E1, E2, and E3 strength was identified from 9 MeV < E(x)< 40 MeV and the effects of differing continua studied

Elastic and inelastic scattering to low-lying states of (58)Ni and (90)Zr using 240-MeV (6)Li

Journals published by the American Physical Society can be found at http://publish.aps.org/Elastic and inelastic scattering of 240-MeV (6)Li particles from (58)Ni and (90)Zr were measured with the multipole-dipole-multipole spectrometer from 4 degrees <= theta(c.m.) <= 43 degrees. The elastic scattering data were fitted with the double-folding model using the density-dependent M3Y NN effective interaction and with a phenomenological Woods-Saxon potential. B(E2) and B(E3) values obtained for low-lying 2(+) and 3(-) states with the double-folding calculations agreed with the adopted values

Giant resonances in (24)Mg and (28)Si from 240 MeV (6)Li scattering

Journals published by the American Physical Society can be found at http://publish.aps.org/Elastic and inelastic scattering of 240 MeV (6)Li particles from (24)Mg and (28)Si were measured with the MDM spectrometer. Optical potential parameters for (6)Li+(24)Mg and (6)Li+(28)Si scattering systems were obtained by fitting elastic scattering with two different folding model potentials as well as W-S potentials. E0-E3 giant resonance strength distributions for (28)Si and (24)Mg were obtained. E0 strength corresponding to 106(-24)(+34)% of the EWSR was identified in (24)Mg and 80(-20)(+35)% was found for (28)Si between E(x)=8.0 to 40.0 MeV

Folding model analysis of 240 MeV (6)Li elastic scattering on (116)Sn and inelastic scattering to low-lying states of (116)Sn

Journals published by the American Physical Society can be found at http://publish.aps.org/Elastic scattering of 240 MeV (6)Li ions from (116)Sn was measured from 4(degrees)<=theta(c.m.)<= 32(degrees). The data were fitted with a Woods-Saxon phenomenological potential and with double folding models using the M3Y NN effective interaction with and without density dependence. DWBA calculations with the fitted parameters were used to calculate cross sections for inelastic scattering to low-lying 2(+)and 3(-) states. B(E2) and B(E3) values were extracted and compared with electromagnetic values and those obtained from alpha inelastic scattering

Intrinsic response time of graphene photodetectors

Graphene-based photodetectors are promising new devices for high-speed optoelectronic applications. However, despite recent efforts, it is not clear what determines the ultimate speed limit of these devices. Here, we present measurements of the intrinsic response time of metal-graphene-metal photodetectors with monolayer graphene using an optical correlation technique with ultrashort laser pulses. We obtain a response time of 2.1 ps that is mainly given by the short lifetime of the photogenerated carriers. This time translates into a bandwidth of ~262 GHz. Moreover, we investigate the dependence of the response time on gate voltage and illumination laser power