In the laboratory, we have two main measurement systems; Positron Annihilation Lifetime Spectroscopy (PALS) as a fast-fast coincidence system and Doppler Broadenning Annihilation Spectroscopy (DBAR). The first measures lifetime of ortho-positronium (o-Ps) as a measure of free volume in materials and the latter measures broadened spectra of annihilation radition that gives information about free volume hole sizes and chemical defects in materials.
We have also Slow Positron Beam System (SLOPOS) to study surfaces and interfaces. We measure depth defect (vacancy and chemical) profile of surfaces changing the positron energy up to 30 keV. We have DBAR or DBES (Doppler Broadening Emission Spectroscopy) ready to run but we are still working on the lifetime spectroscopy.
Fast-Fast Coincidence System:
Positronium Annihilation Lifetime Spectroscopy (PALS, PLTAS)
Doppler Broadenning Annihilation Radiation (DBAR)
Slow Positron Beam System:
Doppler Broadenning Emission Spectroscopy (DBES)
Positron Emission Lifetime Spectroscopy (PELS)(not ready yet)
Laboratory Service Fees
|Positron Annihilation Lifetime Measurement||1||500 Euro|
|Doppler Broadenning Annihilation Radiation Measurement||1||500 Euro|
|Free Volume Analysis Using the Simha Somcynsky Hole Theory||1||750 Euro|
*Single measurement and analysing prices for each sample. If some temperature measurements are requested for the same sample, 50% discount is made for each temperature on the indicated prices.
|Taxes (KDV) is not included.|
|Positron Annihilation Lifetime Measurement (PALS)|
By using Positron Annihilation Lifetime Spectroscopy, we estimate three lifetimes (possible 4 upon request) and their intensities. These are para-positronium, direct annihilation, and ortho-positronium (o-Ps). Using these informations, we calculate free volume hole size and radius values. Additionally, we calculate free volume according to Kobayashi scheme using fv=C I3*vf(tau3).
|Doppler Broadenning Annihilation Lifetime Measurement (DBAR)|
Using Doppler Broadenning Annihilation Spectroscopy, we calculate S and W parameters. The S parameter is calculated as the area under the curve in the central (511 keV peak) region as a contribution of lower momentum divided by the total area in the region of interest (ROI). The W parameter is as the area under the wing regions as a contribution of higher momentum divided by the total area in the ROI. Both parameters have sensitivity to defect type and concentration in materials.
|Free Volume Analysis Using the Simha Somcynsky Hole Theory|
Using Simha-Somscynsky hole theory, for a given PVT data in liquid and glassy states as well crystalline, characteristic parameters; mo, c, s, P*, T*, V*, v*, e* will be calculated and tabulated. The scaled graph of V with respect to P and T or any combination will be drawn upon request. Using these parameters, hole fraction as a measure of free volume (free volume fraction) will be calculated and drawn graphs with respect to T and P upon request. Additional information can be extracted from the SS theory upon request.
In addition to these basic calculations, Tait equations (in forms requested or forms we offer) will be given for PVT scaled data or hole fraction in terms of scaled T and P.
Calculation of additional two different thermodynamic quantities below is required to additional same charge
With available experimental data, some transport properties such as viscosity, ionic conductivity, dielectric relaxation, and diffusion in terms of temperature and pressure can be calculated and will be related with the hole fraction as a measure of free volume. All the information will be tabulated and graphed upon request.
Prof. Dr. Uğur YAHŞİ
Phone: +90 (216) 345 1186 (1348)
Fax: +90 (216) 347 8783
Prof. Dr. Cumali TAV
Phone: +90 (216) 345 1186 (1320)
Marmara University Faculty of Arts and Sciences
Physics Department Office No: C120 Göztepe Campus
34722 Kadıköy, İSTANBUL
This page updated by Pozitron/Pozitronyum Araştırma ve Hizmet Laboratuvarı on 05.12.2018 12:26:31