Modified Millikan capacitor for photoemission studies

Altwegg, L.; Pope, Martin; Arnold, Stephen; Fowlkes, Wm.Y.; Hamamsy, M.A.El

doi:10.1063/1.1136958

Cited by 18 publications

(5 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 20 ps duration, 355 nm laser pulses were generated by a YAG laser, and the PNA compound tetracene was selected for study. The apparatus in which the measurements were made is a variation of the Millikan apparatus for determining the charge of the electron (10), and the same apparatus and method can be used to measure the durations of the light pulses in the femtosecond time range. A patent application covering this invention has already bcen filed by the University.…”

Section: Mechanisms Of Non-linear Photoionization Processes In Pna Somentioning

confidence: 99%

Mechanisms of interaction of radiation with matter. Progress report, July 1, 1992--June 30, 1993

Geacintov¹,

Pope²

1993

Self Cite

View full text Add to dashboard Cite

The combustion of fossil fuels give rise to toxic byproducts which pollute our environment and represent potential hazards to human health. Ionizing radiation from nuclear power plants, radioactive waste dumps, and radon in homes pose yet other environmental health hazards. This project is concerned with the mechanisms by which polynuclear aromatic (PNA) compounds on the one hand, and ionizing radiation on the other, ' cause damage to DNA, the genetic material of the cell. The PNA compounds constitute an important class of environmental pollutants derived from energy-related sources which, upon metabolic activation to diolepoxide derivatives, bind covalently to DNA. These bulky PNA-DNA lesions interfere with the normal DNA replication and transcription processes, and give rise to mutations and the initiation of tumors. Chiral and other stereochemical effects play a key role in determining the biological effects of a given PNA diol epoxide and the potentially mutagenic lesions which are formed. In this project, important breakthroughs have been made by devising new and efficient methods for synthesizing stereochemically pure and precisely positioned PNA diol epoxide-DNA lesions in small DNA fragments : (oligonucleotides). In conjunction with several key collaborators, we have elucidated, for the first time, the structures of three stereoisomeric benzo[a]pyrene diol epoxide-DNA adducts. b The manifestations of these adducts on DNA polymerase fidelity, transcription, and DNA repair are currently being investigated for detailed structure-biological activity correlations. Spectroscopic techniques such as circular dichroism, fluorescence, and photoionization play an important role in the characterizations of the PNA adducts. In this connection, a new method was developed for measuring the lifetimes as well as the energies of short-lived (picosecond duration) electronically excited states (a patent application has been filed). Using this technique, it is proposed that short-lived (15 ps) charge-transfer (CT) states in the PNA compound tetracene are activated by a short (20 ps) laser pulse; an unusual extemal photoemission echo due to the recombination of CT states is observed 85 ps after the pulse. The results obtained by this method are relevant to an understanding of the mechanisms of interaction of ionizing radiation with matter.

show abstract

Section: Mechanisms Of Non-linear Photoionization Processes In Pna Somentioning

confidence: 99%

Mechanisms of interaction of radiation with matter. Progress report, July 1, 1992--June 30, 1993

Geacintov¹,

Pope²

1993

Self Cite

View full text Add to dashboard Cite

show abstract

“…Since the celebrated oil drop experiment of R. A. Millikan in 1909, there has been a number of papers published on the subject of charged particle suspension [1][2][3][4][5]. However, none of these works have addressed the problems of levitating large objects for the purpose of studying drop dynamics or measuring thermophysical properties at high temperatures.…”

Section: Introductionmentioning

confidence: 98%

Development of an electrostatic levitator and containerless processing of metals, alloys, and semiconductors

Rhim

1999

SPIE Proceedings

View full text Add to dashboard Cite

Present capability of the High Temperature Electrostatic Levitator (HTESL) at JPL for the containerless materials processing is described. The capability includes the measurements of various thermophysical properties and the studies of undercooling and nucleation phenomena. The thermophyscial properties that can be measured include the density, the volume expansion, the ratio between the specific heat capacity and the hemispherical total emissivity, the surface tension, the viscosity, the spectral emissivity, and the electrical resistivity. For liquids where the Wiedemann-Franz-Lorenz law applies, their thermal conductivities can be determined indirectly from the electrical resistivities. The capability of determining the statistical nature of nucleation and the Temperature-Time-Transformation (T-T-T) curves has also been demontrated. Experimental results on pure metals, alloys, and semiconductors were use to support the argument.

show abstract

“…(24) to each set of data and solve for + to derive Thus, from measurements of V at two wavelengths, Pope obtained the minimum ionization potential of the particle. Additional photoemission studies were performed by Arnold (1982) and Altwegg et al (1982). Pope's electron emission studies led his associate Arnold (1979) to develop a method for measuring the absolute mass of a single aerosol particle.…”

Section: Photoionization Measurementsmentioning

confidence: 99%