| 1. |
- Andersson, Patrik U, 1970, et al.
(författare)
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Carbon dioxide interactions with crystalline and amorphous ice surfaces
- 2004
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 108:21, s. 4627-4631
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide interactions with crystalline and amorphous water ice have been studied by time-resolved molecular beam techniques. CO2 collisions at thermal kinetic energies with ice in the temperature range 100-160 K result in efficient trapping on the ice surface followed by desorption. The desorption kinetics on crystalline ice at 100-125 K are well described by the Arrhenius equation with an activation energy of 0.22 +/- 0.02 eV and a preexponential factor of 10(13.32+/-0.57) s(-1). Below 120 K, CO2 populates strongly bonded sites on amorphous ice, resulting in surface residence times on the order of minutes at 100 K, and the desorption data can in this case not be explained by a simple first-order process. The results are compared to previous studies of gas-ice interactions, and the implications for heterogeneous processes in the terrestrial atmosphere are discussed.
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| 2. |
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| 3. |
- Dubaric, Ervin, et al.
(författare)
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Monte Carlo simulations of the imaging properties of scintillator coated X-ray pixel detectors
- 2000
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Ingår i: IEEE Nuclear Science Symposium and Medical Imaging Conference. - : IEEE conference proceedings. - 0780365038 ; , s. 6/282-6/285
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Konferensbidrag (refereegranskat)abstract
- The imaging properties of X-ray pixel detectors depend on the quantum efficiency for X-rays, the generated signal for each X-ray photon and the distribution of the generated signal between different pixels. In a scintillator coated device the signal is generated both by X-ray photons captured in the scintillator and by X-ray photons captured directly in the semiconductor. Hence, the signal-to-noise ratio (SNR) in the image is then a function of the number of photons captured in each of these processes, and the yield of each process, in terms of electron-hole pairs (EHPs) produced in the semiconductor. The full process from the absorption of the X-ray photon to the final signal read out from the detector has been simulated with a combination of the Monte Carlo program MCNP and the commercial carrier transport simulation tool MEDICI. An in house program calculating the light transport between the scintillator and the semiconductor serves as a link
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| 5. |
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| 6. |
- Gustafsson, Mats, et al.
(författare)
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High-resolution digital transmission microscopy: a Fourier holography approach
- 2004
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Ingår i: Optics and Lasers in Engineering. - 0143-8166. ; 41:3, s. 553-563
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Tidskriftsartikel (refereegranskat)abstract
- A spherical reference field is used to construct a digital holographic system with a demonstrated resolution up to 228 line pairs per mm. The reference field originates from a GRIN lens placed 1 mm from the illuminated object. This allows the use of a standard sensor to record the hologram with the required numerical aperture. The image is determined by evaluation of the Rayleigh–Sommerfeld diffraction integral that relates the object field in the image plane to the object field in the sensor plane. Experimental results are given for two charge coupled device sensors and one complementary metal-oxide-semiconductor active pixel sensor.
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| 7. |
- Gustafsson, Mats, et al.
(författare)
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High resolution digital transmission microscopy : a Fourier holography approach
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A spherical reference field is used to construct a digital holography system with a demonstrated resolution down to 228 line pairs per mm. The reference field origin from a GRIN lens placed 1mm from the illuminated object. This allows the use of a standard sensor to record the hologram with the required numerical aperture. The image is determined by evaluation of the Rayleigh-Sommerfeld diffraction integral that relates the object field in the image plane to the object field in the sensor plane. Experimental results are given for two charge couple device sensors and one complementary metaloxide- semiconductor active pixel sensor.
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| 8. |
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| 9. |
- Landin, L., et al.
(författare)
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Interband transitions in InAs quantum dots in InP studied by photoconductivity and photoluminescence techniques
- 2004
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Ingår i: Journal of Applied Physics. - Melville : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 95:12, s. 8007-8010
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed investigation of the interband optics of self-assembled InAs dots embedded in a matrix of InP. In photoconductivity (PC) measurements, we observe optical processes related to the dots and a wetting layer, band-to-band excitation of the InP barrier, as well as to an interesting As-related impurity. In particular, the PC measurements reveal the electronic structure of the dots and strongly suggest that an Auger effect is involved in forming the PC signal. Comparing the PC and photoluminescence (PL) signals, we observe that the fundamental transition is not observed in PC, which we interpret in terms of Pauli blocking due to electrons populating the ground state of the dots. In general, it is demonstrated that the PC technique is in many respects complementary to PL and gives additional insight into the electronic structure of quantum dots.
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| 10. |
- Pettersson, Håkan, et al.
(författare)
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Intersubband photoconductivity of self-assembled InAs quantum dots embedded in InP
- 2004
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 95:4, s. 1829-1831
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Tidskriftsartikel (refereegranskat)abstract
- The results from photoconductivity (PC) measurements on InAs dots embedded in InP are presented. The PC technique is recently applied to the study of InAs dots embedded in matrices of GaAs and Al0.3Ga0.7As matrix, respectively. It is demonstrated that this technique reveals important new physical insight into the electronic structure of the InAs/InP dots, information that cannot easily be obtained by other techniques.
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