| 1. |
- Adcox, K, et al.
(author)
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PHENIX detector overview
- 2003
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 499:2-3, s. 469-479
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Journal article (peer-reviewed)abstract
- The PHENIX detector is designed to perform a broad study of A-A, p-A, and p-p collisions to investigate nuclear matter under extreme conditions. A wide variety of probes, sensitive to all timescales, are used to study systematic variations with species and energy as well as to measure the spin structure of the nucleon. Designing for the needs of the heavy-ion and polarized-proton programs has produced a detector with unparalleled capabilities. PHENIX measures electron and muon pairs, photons, and hadrons with excellent energy and momentum resolution. The detector consists of a large number of subsystems that are discussed in other papers in this volume. The overall design parameters of the detector are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Adler, SS, et al.
(author)
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PHENIX on-line systems
- 2003
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 499:2-3, s. 560-592
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Journal article (peer-reviewed)abstract
- The PHENIX On-Line system takes signals from the Front End Modules (FEM) on each detector subsystem for the purpose of generating events for physics analysis. Processing of event data begins when the Data Collection Modules (DCM) receive data via fiber-optic links from the FEMs. The DCMs format and zero suppress the data and generate data packets. These packets go to the Event Builders (EvB) that assemble the events in final form. The Level-1 trigger (LVL1) generates a decision for each beam crossing and eliminates uninteresting events. The FEMs carry out all detector processing of the data so that it is delivered to the DCMs using a standard format. The FEMs also provide buffering for LVL1 trigger processing and DCM data collection. This is carried out using an architecture that is pipelined and deadtimeless. All of this is controlled by the Master Timing System (MTS) that distributes the RHIC clocks. A Level-2 trigger (LVL2) gives additional discrimination. A description of the components and operation of the PHENIX On-Line system is given and the solution to a number of electronic infrastructure problems are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
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| 4. |
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| 5. |
- Terazono, Y., et al.
(author)
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Photonic control of photoinduced electron transfer via switching of redox potentials in a photochromic moiety
- 2004
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In: Journal of Physical Chemistry B. ; 108:6, s. 1812-1814
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Journal article (peer-reviewed)abstract
- A porphyrin (P) has been covalently linked to a photochromic dihydroindolizine moiety (DHI) to form a P-DHI dyad. When the dihydroindolizine is in its closed, spirocyclic form (DHIc), the photophysics of the attached porphyrin are unaffected. Irradiation with UV light opens the photochromic moiety to the betaine form (DHIo), which has a significantly higher reduction potential than DHIc. Light absorption by the porphyrin moiety of P-DHIo is followed by rapid (50 ps) photoinduced electron transfer to yield the P.+-DHIo(.-) charge-seperated state. This state recombines in 2.9 ps to give the ground state. Irradiation of P-DHIo with light at wavelengths > 590 nm induces photoisomerization back to P-DHIc. Thermal closing can also be achieved. Thus, light is used to switch photoinduced electron transfer on or off. These principles may be useful in the design of molecular optoelectronic devices.
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| 6. |
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| 7. |
- Andreasson, Joakim, 1973, et al.
(author)
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Photoinduced hole transfer from the triplet state in a porphyrin-based donor-bridge-acceptor system
- 2003
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In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 107:42, s. 8825-8833
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Journal article (peer-reviewed)abstract
- The triplet excited-state deactivation of a gold porphyrin (AuP) in porphyrin-based donor-bridge-acceptor (D-B-A) systems has been studied. The results from room temperature and 80 K measurements are presented. The primary objectives have been to investigate whether electrons/electron holes or excitation energy could be transferred from (AuP)-Au-3 to the appended zinc porphyrin (ZnP) in the dimers. As the bridging chromophores in our D-B-A systems separate the ZnP and AuP moieties by 19 A edge-to-edge, we do not expect a significant contribution to either electron or energy transfer from a direct (through space) exchange mechanism. This gives us the opportunity to scrutinize how the bridging chromophores influence the transfer reactions. The results show that quenching of (AuP)-Au-3 occurs with high efficiency in the dimers that are connected by fully conjugated bridging chromophores, whereas no quenching is observed when the conjugation of the bridge is broken. We also observed that the decay of (AuP)-Au-3 is complex at temperatures below 110 K. In addition to the two previously published lifetimes on the order of some 10-100 mus, we have found a third lifetime on the nanosecond time scale.
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| 8. |
- Andreasson, Joakim, 1973, et al.
(author)
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The gold porphyrin first excited singlet state
- 2002
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In: Photochemistry and Photobiology. - 0031-8655 .- 1751-1097. ; 76:1, s. 47-50
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Journal article (peer-reviewed)abstract
- Gold porphyrins are often used as electron-accepting chromophores in artificial photosynthetic constructs. Because of the heavy atom effect, the gold porphyrin first-excited singlet state undergoes rapid intersystem crossing to form the triplet state. The lowest triplet state can undergo a reduction by electron donation from a nearby porphyrin or another moiety. In addition, it can be involved in triplet-triplet energy transfer interactions with other chromophores. In contrast, little has been known about the short-lived singlet excited state. In this work, ultrafast time-resolved absorption spectroscopy has been used to investigate the singlet excited state of Au(III) 5,15-bis(3,5-di-t-butylphenyl)-2,8,12,18,-tetraethyl-3,7,13,17-tetrameth ylporphyrin in ethanol solution. The excited singlet state is found to form with the laser pulse and decay with a time constant of 240 fs to give the triplet state. The triplet returns to the ground state with a lifetime of 400 ps. The lifetime of the singlet state is comparable with the time constants for energy and photoinduced electron transfer in some model and natural photosynthetic systems. Thus, it is kinetically competent to take part in such processes in suitably designed supermolecular systems.
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| 9. |
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| 10. |
- Liddell, P. A., et al.
(author)
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Photoinduced electron transfer in a symmetrical diporphyrin-fullerene triad
- 2004
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In: Physical Chemistry Chemical Physics. ; 6:24, s. 5509-5515
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Journal article (peer-reviewed)abstract
- Two triad molecules consisting of either two zinc, or two free-base porphyrins symmetrically joined to a fullerene via phenyleneethynylene-containing linkages have been synthesized, and their photochemistry investigated. In the zinc form of the triad, P-Zn-C-60-P-Zn, excitation of a zinc porphyrin in 2-methyltetrahydrofuran solution is followed by photoinduced electron transfer to the fullerene with a time constant of 20 ps. The resulting P-Zn(.+)-C-60(.-)-P-Zn charge-separated state is formed with a quantum yield of 98% and has a lifetime of 820 ps. The first excited singlet state of the free-base analog gives the P-2H(.+)-C-60(.-)-P-2H charge-separated state with a time constant of 200 ps and a yield of 98%. The charge-separated state decays with a lifetime of 2.8 ns. The difference in the rates of photoinduced electron transfer is consistent with reaction in the normal region of the Marcus-Hush relationship of transfer rate and driving force, and charge recombination is consistent with Marcus-Hush inverted behavior. The presence of the two porphyrin electron donors in these triads enhances the absorption cross section for light collection, and the molecular framework employed could be used to prepare molecules with enhanced energy conversion or optoelectronic properties.
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