Photoelectron Angular Distributions for Two-photon Ionization of Helium by Ultrashort Extreme Ultraviolet Free Electron Laser Pulses

Phase-shift differences and amplitude ratios of the outgoing $s$ and $d$ continuum wave packets generated by two-photon ionization of helium atoms are determined from the photoelectron angular distributions obtained using velocity map imaging. Helium atoms are ionized with ultrashort extreme-ultraviolet free-electron laser pulses with a photon energy of 20.3, 21.3, 23.0, and 24.3 eV, produced by the SPring-8 Compact SASE Source test accelerator. The measured values of the phase-shift differences are distinct from scattering phase-shift differences when the photon energy is tuned to an excited level or Rydberg manifold. The difference stems from the competition between resonant and non-resonant paths in two-photon ionization by ultrashort pulses. Since the competition can be controlled in principle by the pulse shape, the present results illustrate a new way to tailor the continuum wave packet.Comment: 5 pages, 1 table, 3 figure

Iron-filled multiwalled carbon nanotubes surface-functionalized with paramagnetic Gd (III): A candidate dual-functioning MRI contrast agent and magnetic hyperthermia structure

The authors are grateful for the financial support from the Engineering and Physical Science Research Council, UK

Time-resolved photoluminescence study on concentration quenching of a red emitting tetraphenylchlorin dye for organic electroluminescent devices

Time-resolved photoluminescence (PL) of a red emitting dye, tetraphenylchlorin (TPC), doped in poly(methyl methacrylate) (PMMA) at various concentrations was studied to clarify the mechanism of concentration quenching often observed in organic electroluminescence devices. At doping concentrations lower than 10(-2) mol/L, PL lifetimes of TPC were relatively constant (similar to 10ns) and equal to that of TPC in dilute solution. At doping concentrations higher than 10-2 mol/L, PL lifetime decreased rapidly with increasing concentration, down to 2 ns at 8 x 10(-2) mol/L. This decrease in PL lifetime was related to the concentration quenching of TPC monomer emission by the increasing number of TPC dimer sites formed at such higher concentrations. Our experimental results of concentration-dependence trapping agree fairly well with the theoretical model of trapping by dimers reported in literature. (c) 2005 Elsevier B.V. All rights reserved.</p

Pengembangan Lembar Kerja Peserta Didik (Lkpd) Berbasis Inkuiri pada Materi Sistem Sirkulasi di SMA Negeri 5 Palangka Raya

LKPD merupakan salah satu sumber belajar yang dapat dikembangkan oleh pendidik sebagai Fasilitator dalam kegiatan pembelajaran. LKPD merupakan lembaran-lembaran berisi tugas yang dikerjakan oleh peserta didik, berisi petunjuk, langkah-langkah untuk menyelesaikan suatu tugas berupa teori ataupun praktik. Keterbatasan LKPD yang digunakan di sekolah menyebabkan peserta didik kesulitan memahami praktikum dan menjadi lebih pasif, dimana LKPD di sekolah hanya berisikan topik, tujuan, cara kerja secara singkat, dan beberapa soal evaluasi. Tujuan penelitian ini adalah untuk mengetahui kualitas LKPD berbasis Inkuiri yang dikembangkan dan untuk mengetahui respon peserta didik. Pengembangan LKPD berbasis inkuiri menggunakan metode penelitian dan pengembangan atau research &amp; development (R&amp;D) dengan model ADDIE (Analysis, Design, Development, Implementation and Evaluations). LKPD hasil pengembangan divalidasi oleh ahli materi, ahli media &amp; pembelajaran, ahli bahasa dan guru, serta diuji pada peserta didik untuk melihat responsnya. Instrumen yang digunakan dalam penelitian ini berupa angket. Angket digunakan pada validasi ahli, respons guru, dan respons peserta didik untuk mengumpulkan data. Data yang didapat dianalisis menggunakan rumus kriteria kualitas. Hasil penelitian menunjukkan bahwa LKPD berbasis inkuiri hasil pengembangan layak untuk digunakan berdasarkan validasi oleh ahli materi sebesar 65% termasuk kriteria baik, ahli media &amp; pembelajaran sebesar 96% termasuk kriteria sangat baik, ahli bahasa sebesar 95% dengan kriteria sangat baik dan respons guru sebesar 77% dengan kriteria sangat baik, dan respons peserta didik terhadap LKPD yang dikembangkan sebesar 85% dengan kriteria sangat menarik &amp; sangat membantu