Cross-section Σa Research Articles

High-temperature-insensitivity high-power Yb-doped fiber laser directly in-band pumping by 1018 nm laser diodes.

In this Letter, we demonstrate a high-power ytterbium-doped fiber laser (YDFL) based on a directly in-band pumping scheme (DIPS) which employs 1018 nm laser diodes (LDs) as pump sources. The wavelength of the LDs is designed theoretically, considering the distribution of Yb3+ absorption cross section (σa) as well as quantum defect (QD). The flat distribution of σa around 1018 nm ensures excellent temperature insensitivity and flexibility for the YDFL. Besides, lower QD and more compact structure promise higher optical-to-optical (O-O) and electrical-to-optical (E-O) efficiencies. Based on the experimental setup, as the cooling temperature of the 1018 nm LDs ranges from 6 to 23°C, an output power of 2 kW level is achieved that varies by only 2.01% without adjusting the operating current of the LDs subjectively. The output power is then scaled up to 5 kW level. Furthermore, there is a great potential to achieve higher output power and E-O efficiency in YDFLs based on the DIPS.

Efficiency scale for scattering luminescent particles linked to fundamental and measurable spectroscopic properties

Comparing the performance of molecular and nanoscale luminophores and luminescent micro- and nanoparticles and estimating achievable signal amplitudes and limits of detection requires a standardizable intensity scale. This initiated the development of the relative MESF (number of molecules of equivalent soluble fluorochromes) and ERF (equivalent reference fluorophores) scales for flow cytometry and fluorescence microscopy. Both intensity scales rely on fluorescence intensity values assigned to fluorescent calibration beads by an intensity comparison to spectrally closely matching fluorophore solutions of known concentration using a spectrofluorometer. Alternatively, the luminophore or bead brightness (B) can be determined that equals the product of the absorption cross section (σa) at the excitation wavelength (σa(λex)) and the photoluminescence quantum yield (Φpl). Thereby, an absolute scale based on fundamental and measurable spectroscopic properties can be realized which is independent of particle size, material, and luminophore staining or labeling density and considers the sensitivity of the optical properties of luminophores to their environment. Aiming for establishing such a brightness scale for light-scattering dispersions of luminescent particles with sizes exceeding a few ten nanometers, we demonstrate how the brightness of quasi-monodisperse 25 nm, 100 nm, and 1 µm sized polystyrene particles (PSP), loaded with two different dyes in varying concentrations, can be obtained with a single custom-designed integrating sphere setup that enables the absolute determination of Φpl and transmittance and diffuse reflectance measurements. The resulting Φpl, σa(λex), imaginary parts of the refractive index, and calculated B values of these samples are given in dependence of the number of incorporated dye molecule per particle. Finally, a unitless luminescence efficiency (LE) is defined allowing for the direct comparison of luminescence efficiencies of particles with different sizes.

Development of high-density radiation shielding materials containing BaSO4 and investigation of the gamma-ray attenuation properties

The high-density shielding materials containing higher percentage (>80%) of BaSO4 have been developed and their gamma-ray attenuation parameters have been investigated. Three samples have been prepared [Sample-1 (83.75%), Sample-2 (84.75%), and Sample-3 (82.75%)], their elemental composition has been determined by the EDX method, and the density has been measured experimentally for Sample-1 (3.362 g/cm3), Sample-2 (3.365 g/cm3), and Sample-3 (3.358 g/cm3). The mass attenuation coefficients (μ/ρ) have been calculated analytically in order to generate a database for the photon energy range from 1keV to 100MeV using WinXcom software. For validation, this parameter has been measured experimentally for gamma-ray emitted from 133Ba radioactive sources using HPGe detector (with relative efficiency ≈20% relative to a 3"×3"NaI(Tl) detector, and resolution 2.3keV at 1.33MeV γ-lines). The linear attenuation coefficient (μ), total atomic cross section (σa), total electronic cross section (σe), effective atomic number (Zeff), effective electron density (Neff), and relaxation length (λ) have been calculated for the same energy range. All parameters have been compared with the values for five different concretes namely barite, serpentine, ilmenite-magnetite, ordinary concrete, and basalt-magnetite. Transmission graphs have been drawn for some widely used radioactive sources. Sample-2 with the highest density (3.365 g/cm3) and comprising relatively higher atomic number elements is found to be the most effective shield for gamma-ray attenuation.

Gamma-ray shielding studies on borate glasses containing BaO, Bi2O3, and PbO in different concentrations

Mass attenuation coefficients (μm), half value layer (HVL), effective atomic cross sections (σa), effective atomic numbers (Zeff) and effective electron densities (Neff) of borate glasses containing different concentrations of BaO, Bi2O3, and PbO (20–50% by mole) were obtained in the energy range of 10 keV–10 MeV using MCNPX code, XCOM and XMuDat programs, Auto-Zeff software and linear interpolation method. The simulated and calculated results were in good agreement with the experimental data with differences of ≤ ± 11%. It was found that σa and Zeff of glass samples improve by increasing their BaO, PbO and Bi2O3 contents, while increasing these contents to the same fraction has no significant effect on μm values in the energy range of 0.3–6 MeV, where the Compton Effect takes over as dominant process. In addition, the μm and σa values of glasses decreased with photon energy and bismuth oxide borate glass obtained the highest values of μm and σa. Also, HVL values of the studied glasses decreased with the increase in their densities. The 50Bi2O3:50B2O3 glass system had the highest Zeff value of 55.60 at the 30 keV photon energy. Above 0.4 MeV photon energy, Neff values were independent of the metal oxides contents. The Neff values of the studied glass systems varied in the range of 2.77 × 1023 – 9.10 × 1023 electron/g.

Quantum approach for nanoparticle fluorescence by sub-ns photon detection.

Well defined detection and analysis of nanoparticle-sized samples such as extracellular vesicles or viruses may be important for potential disease diagnostics. However, using conventional flow-cytometry optical methods to evaluate such small particles is quite challenging. The reason is that the particle is smaller than the diffraction limit, making detection difficult. An alternative approach is fluorescence detection via conjugated fluorochromes attached to the nanoparticles; the challenge in this case is the limitation imposed upon detection of a very small number of emitted photons buried in high background photon counts. Emitted fluorescence is described by the well-known equation kf = σa I Q, which describes the emitted fluorescence rate (kf) (photons/s) as the multiplication of molecular absorption cross section(σa), excitation intensity (I), and quantum yield (Q). In addition, the excitation rate is equal to 1/t, which is the inverse of the lifetime of several ns representing the most typical conjugated fluorescent molecules used in flow cytometry. We recently developed a sub-ns photon sensor that is faster than most fluorescence lifetimes, since sub-ns speed is a critically important parameter for the separation of individual emitted photons. Based on our observation of fluorescence and background levels on typical commercial flow cytometers it is evident that a significant component of the background is induced by water-molecular vibrations. Therefore, understanding what constitutes all the components that contribute to the signals we measure in flow cytometry would help in defining what we currently call "background signals." We attempted to define a theoretical model to try to unravel these issues. This model was based on use of a reflective dry surface in the absence of water molecules. Our objective was to determine if it is possible to minimize background and enhance signal, and to provide valuable information on the contributing components of the signals collected. In order to test this model, we tested a single dried particle 50 nm in diameter on a reflective surface with minimum background. While this is clearly not a standard biological system, our results suggest that this quantum approach closely follows established photon base theory. Our goal was to define the parameters for practical nanoparticle-fluorescence analysis while enhancing our knowledge of the contribution of background properties.

Photon Interaction Properties of Different Bones from Human Body Using MCNPX, WinXCom, XMuDat, and Auto-Zeff Programs

Abstract The human body consists of various bones with different elemental compositions and densities. The mass attenuation coefficients (μm), effective atomic and electronic cross sections (σa and σe), effective atomic numbers and electron densities (Zeff and Neff), and computed tomography (CT) numbers of the human body’s various bones have been determined for the main gamma rays of 67gallium, 153samarium, 99mtechnetium, 201thallium, 131iodine radionuclides and gamma rays from positron annihilation. To calculate these parameters, MCNPX code, WinXCom, and XMuDat computer programs and also the Auto-Zeff software and interpolation method have been used. The results of the MCNPX code were in good agreement with the WinXCom and XMuDat programs with differences of ≤4.42 %. It was found that the σa, σe, Zeff, and CT number parameters decrease as photon energy increases and the density of bone samples decreases. The μm and Neff values decrease with the increase in photon energy based on the results. Furthermore, they are approximately independent of the bone sample density. Of all the bone types, the σa, σe, Zeff, and CT number values of cortical bone are the greatest ones, while those of spongiosa are the lowest. Observed good agreement reveals that the chosen Monte Carlo code and computer programs could be useful to calculate the photon interaction characteristics of different bone types.

Ion beam irradiation of ABO4 compounds with the fergusonite, monazite, scheelite, and zircon structures

AbstractThe effects of irradiation on CaWO4, SrWO4, BaWO4, YVO4, LaVO4, YNbO4, and LaNbO4 were investigated on thin crystals using 1.0 MeV Kr ions at 50‐1000 K. All of the ABO4 compounds can be amorphized with calculated damage cross sections (σa = 1/Fc0) in the range of ~0.30‐1.09 × 10‐14 cm2 ion−1 at zero Kelvin. The analysis of fluence‐temperature data returned critical temperatures for amorphization (Tc) of 311 ± 1, 358 ± 90, 325 ± 19, 415 ± 17, 541 ± 6, 636 ± 26, and 1012 ± 1 K, respectively, for the compounds listed above. Compared with previous in situ irradiation of ABO4 orthophosphate samples using 0.8 MeV Kr ions, the Tc values of LaVO4 and YVO4 are higher than those of LaPO4 and YPO4 by 82 K and 124 K, respectively. The Tc values of the three scheelite structures, CaWO4, SrWO4, and BaWO4, indicate that they are the most radiation tolerant compounds under these conditions. The A‐B cation anti‐site energies, EfAB, determined by DFT range from 2.48 to 10.58 eV and are highly correlated with the A‐B cation ionic radius ratio, rA/rB, but are not correlated with Tc across the different structure types, suggesting that the formation and migration energies of Frenkel defects play a more important role in damage recovery in these compounds. We also discuss the role of cation and anion charge/iconicity as determined by DFT. ABO4 compounds with the zircon structure and B = P or V have a distinct advantage over those with B = Si as the damaged regions do not appear to be significantly affected by polymerization of (PO4)3− or (VO4)3− groups which might stabilize the amorphous fraction and ultimately lead to phase separation as observed in zircon (ZrSiO4).

Gamma-ray shielding properties of phosphate glasses containing Bi2O3, PbO, and BaO in different rates

Glass-based materials are one of the most common shielding materials. Phosphate glasses have unique properties that make them useful for some technical and industrial applications. The mass attenuation coefficients (μm), effective atomic cross sections (σa), effective atomic numbers and electron densities (Zeff and Neff) of phosphate glasses containing different concentrations of Bi2O3, PbO, and BaO (30–70% by weight) have been determined in the energy range of 10 keV–10 MeV. To calculate these parameters, XCOM and XMuDat computer programs and also the Auto-Zeff software and interpolation method have been used. The results of XCOM, XMuDat and Auto-Zeff programs were in good agreement. It was found that the μm and σa parameters decrease as the photon energy increase. Also, the σa and Zeff values improve by increasing the Bi2O3, PbO and BaO contents, while increasing these contents to the same fraction has no significant effect on μm in the energy range of 0.4–4 MeV, where the Compton Effect takes over as dominant process. Furthermore, the Neff is approximately independent of metal oxides concentrations. Wherever possible, the calculated values were compared with the experimental data.

Gamma ray shielding characteristics of Sn-20Bi and Sn-20Bi-0.4Cu lead-free alloys

As a result of the expansion in the different uses of gamma ray sources and as a result of the harmful effects of radiation exposure, scientific research remains in need of finding and developing materials used as radiation shields. In the present study, shielding parameters of Sn-20Bi (SB) and Sn-20Bi-0.4Cu (SBC) lead-free alloys solidified with and without the effect of a rotating magnetic field (RMF) have been studied. Gamma ray mass attenuation coefficient (μt/ρ) was measured experimentally for the studied alloys at photon energy of 356, 511, 662, 1173, 1274, and 1332 KeV. The experimental μt/ρ values were compared with the calculated values by using the WinXCom and MCNP5 programs for alloys solidified without RMF. Besides, WinXCom and MCNP5 were used to calculate μt/ρ for gamma ray photons of energy range of 10−3-102 MeV. The atomic and electronic cross sections (σa and σe) and hence the effective atomic number (Zeff) and effective electron density (Neff) were calculated. The mean free path (MFP) of photons was calculated and introduced to MCNP5 input file to calculate the gamma ray energy buildup factor (EBF). The results of μt/ρ are shown to be highly compatible between the theoretical WinXCom and simulated MCNP5 programs and with the experimental values. The results of the shielding parameters confirm that the alloys under study are good shielding materials against gamma rays.

Gamma-ray shielding properties for silicate glasses containing Bi2O3, PbO, and BaO

Introduction: With the extensive application of radiation sources and radioactive materials in various fields, the study of attenuation and absorption of X-rays and gamma-rays in several materials has become an essential and interesting field of research. Glass materials are possible alternatives of concretes for radiation-shielding materials. Materials and Methods: The mass attenuation coefficients (µm), effective atomic cross section (σa), effective atomic number (Zeff) and effective electron density (Neff) of silicate glasses containing different concentrations of Bi2O3, PbO, and BaO (30–70% by weight) were obtained using MCNP-4C code, XCOM and XMuDat programs, in the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Zeff and Neff. The Auto-Zeff software was used to determine the Zeff as well. Results: The MCNP-4C Code, XCOM and XMuDat programs and Auto-Zeff results were in good agreement. It was found that the µm and σa values decrease with photon energy. Also the results indicate that σa and Zeff of glasses improve by increasing their Bi2O3, PbO and BaO contents, while increasing these contents to the same fraction has no significant effect on µm in the energy range of 0.3–5 MeV, where the Compton Effect takes over as dominant process and Neff do not follow certain rule. Above 0.1 MeV, lead oxide silicate glass showed the highest values of Zeff and σa. Conclusion: Observed good agreement indicates that the chosen Monte Carlo code and computer programs may be useful to calculate the gamma-ray shielding characteristics of different glass systems, particularly in cases where no experimental data exist.

Determination of gamma-ray shielding properties for silicate glasses containing Bi2O3, PbO, and BaO

The mass attenuation coefficients (μm), effective atomic cross section (σa), effective atomic number (Zeff) and effective electron density (Neff) of silicate glasses containing different concentrations of Bi2O3, PbO, and BaO (30–70% by weight) were obtained using MCNP-4C code, XCOM and XMuDat programs, in the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Zeff and Neff. The Auto-Zeff software was used to determine the Zeff as well. The MCNP-4C Code, XCOM and XMuDat programs and Auto-Zeff results were in good agreement. It was found that the μm and σa values decrease with photon energy. Also the results indicate that σa and Zeff of glasses improve by increasing their Bi2O3, PbO and BaO contents, while increasing these contents to the same fraction has no significant effect on μm in the energy range of 0.3–5 MeV, where the Compton Effect takes over as dominant process and Neff do not follow certain rule. Above 0.1 MeV, lead oxide silicate glass showed the highest values of Zeff and σa. Wherever possible, the simulated and calculated values were compared with experimental data.

Mass attenuation coefficients and effective atomic numbers of biological compounds for gamma ray interactions

The mass attenuation coefficients (μ/ρ) for some enzymes, proteins, amino acids and fatty acids were measured at 122, 356, 511, 662, 1170, 1275 and 1330keV photon energies, by performing transmission experiments using 57Co, 133Ba, 137Cs, 60Co and 22Na sources collimated to produce 0.52cm diameter beams. A NaI (Tl) scintillation detector with energy resolution 8.2% at 663keV was used for detection. The experimental values of (μ/ρ) were then used to determine the atomic cross section (σa), electronic cross section (σe), effective atomic number (Zeff) and electron density (Neff). It was observed that (μ/ρ), σa and σe decrease initially and then tends to be almost constant at higher energies. Values of Zeff and Neff were observed roughly constant with energy. The deviations in experimental results of radiological parameters were believed to be affected by physical and chemical environments. Experimental results of radiological parameters were observed in good agreement with WinXCom values.

Optical Properties and Amplified Spontaneous Emission of Novel MDMO-PPV/C500 Hybrid.

The influence of the solvent nature on optical properties of poly[2-methoxy-5-3,7-dimethyloctyloxy-1,4-phenylenevinylene] (MDMO-PPV)/Coumarine 500 (C500) have been investigated. In addition, the amplified spontaneous emission (ASE) from MDMO-PPV and efficient energy transfer between the MDMO-PPV and C500 has been verified. The MDMO-PPV was dissolved in aromatic and nonaromatic solvents, while the solution blending method was employed to prepare the MDMO-PPV:C500 hybrid. The quantum yield of the MDMO-PPV was found to increase with the reduction of a few factors such as polarity index of the solvent, absorption cross section (σa), emission cross section (σe), and extinction coefficient (εmax). The fluorescence spectra of the MDMO-PPV appears from two vibronic band transitions (0-0, 0-1) and the ASE occurs at 0-1 transition, which was verified by the ASE from MDMO-PPV. The MDMO-PPV in toluene exhibited the best ASE efficiency due to its high quantum yield compared with other solvents. Strong overlap between the absorption spectrum of MDMO-PPV and emission spectrum of C500 confirmed the efficient energy transfer between them. Moreover, the ASE for energy transfer of the MDMO-PPV:C500 hybrid was proved.

English

The total and partial mass attenuation coefficients for different Maraging steel compositions have been determined by using the WinXCom and MCNP5 programs. The effective atomic number, Zeff, and effective electron number, Neff, for the studied steels have been determined via the total mass attenuation coefficients μ/ρ, the total atomic and electronic cross sections (σa and σe) of the investigated steels. The shielding parameters μ/ρ, Zeff, and Neff have been calculated at the incident photon energy range of 1 keV–100 MeV. The calculated results of total and partial mass attenuation coefficients, the effective atomic number and the effective electron number by using MCNP5 program were found to be in good agreement with the theoretical results of the WinXCom program. The calculated data clarify that the different steel compositions under investigation have so far the same ability of gamma attenuation. Also, it was found that the total mass attenuation coefficients of the different investigated steels (cobalt free-Maraging steels) are comparable to the C250 standard steel (cobalt Maraging steel). Key words: Gamma rays, shielding, mass attenuation coefficients, effective atomic number, effective electron number.

Gamma ray interaction studies of organic nonlinear optical materials in the energy range 122 keV–1330 keV

The mass attenuation coefficients (μm) for organic nonlinear optical materials measured at 122–1330keV photon energies were investigated on the basis of mixture rule and compared with obtained values of WinXCOM program. It is observed that there is a good agreement between theoretical and experimental values of the samples. All samples were irradiated with six radioactive sources such as 57Co, 133Ba, 22Na, 137Cs, 54Mn and 60Co using transmission arrangement. Effective atomic and electron numbers or electron densities (Zeff and Neff), molar extinction coefficient (ε), mass energy absorption coefficient (μen/ρ) and effective atomic energy absorption cross section (σa,en) were determined experimentally and theoretically using the obtained μm values for investigated samples and graphs have been plotted. The graph shows that the variation of all samples decreases with increasing photon energy.

Photon interaction study of organic nonlinear optical materials in the energy range 122–1330 keV

In the present study, the mass attenuation coefficient (µm) of six organic nonlinear optical materials has been calculated in the energy range 122–1330keV and compared with the obtained values from the WinXCOM program. It is found that there is a good agreement between theoretical and experimental values (<3%). The linear attenuation coefficients (µ) total atomic cross section (σt, a), and total electronic cross section (σt, el) have also been calculated from the obtained µm values and their variations with photon energy have been plotted. From the present work, it is observed that the variation of obtained values of µm, µ, σt, a, and σt, el strongly depends on the photon energy and decreases or increases due to chemical composition and density of the sample. All the samples have been studied extensively using transmission method with a view to utilize the material for radiation dosimetry. Investigated samples are good material for radiation dosimetry due their low effective atomic number. The mass attenuation coefficient (µm), linear attenuation coefficients (µ), total atomic cross section (σt, a), total electronic cross section (σt, el), effective atomic numbers (Zeff), molar extinction coefficient (ε), mass energy absorption coefficient (µen/ρ) and effective atomic energy absorption cross section (σa, en) of all sample materials have been carried out and transmission curves have been plotted. The transmission curve shows that the variation of all sample materials decreases with increasing photon energy.

Importance of photo atomic cross section for studying physical properties of different types of soil

The objective of this work is focused on development of a classification tool for identifying soil texture based on photon attenuation interaction atomic cross‐section data. The total mass attenuation coefficients (μ/ρ) and the atomic cross sections (σa) of soils with different textures have been calculated for total photon interactions in a wide energy range (1 keV to 100 GeV). The values of these parameters have been found to change with soil composition in low energies (1–100 keV), whereas their behavior has been found to be similar at all energies. Slight differences were observed in σa in the energy range of 0.01 to 10 MeV and more pronounced ones from 10 MeV to 100 GeV. Regarding μ/ρ, only small differences were observed among soils for all the energy range investigated. Differences between μ/ρ and σa considering different proportions of Fe2O3 and SiO2 were also observed. The reported data should be useful for studying soil texture according photo attenuation. The results of this work can stimulate research for all types of soil texture. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates

We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), d-Galactose (C6H12O6), Inositol (C6H12O6), d-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

Photoluminescence features of Ho3+ ion doped PbO–Bi2O3 borophosphate glass systems

Spectroscopic and physical properties of Ho3+ doped multi-component glass systems in varying molar compositions of xBi2O3–(50−x) PbO–25MgHPO4–24B2O3–1Ho2O3 (where x=10, 20, 30, and 40) have been investigated. Optical absorption spectra have been used to determine Racah coefficients (E1, E2 and E3), Slater Condon parameters (F2, F4 and F6), spin–orbit coupling parameters (ξ4f), and configuration interaction parameters (α and β). The ratios of E1/E3 and E2/E3 do not deviate much from the hydrogenic ratios. Optical basicity of the glasses is estimated. The Judd–Ofelt parameters (Ω2,Ω4 and Ω6) were computed from the intensities of the energy levels. The radiative lifetimes (τR), branching ratios (β) and absorption cross sections (σa) were evaluated for the lasing levels 5I8→5G6, 5F2, 5F3, 5F4, 5F5, 5I6, and 5I7. The emission cross sections (σe) for the significant lasing transitions 5F4→5I8, 5F5→5I8 and 5S2→5I7 evaluated from the photoluminescence spectra are reported. The lasing potencies estimated for all the glasses under study indicate lasing action in the cw as well as in pulsed regime.

Experimental and theoretical investigations on photoabsorption and photoionization of trimethylphosphate in the vacuum-ultraviolet energy range

In this work, we report a joint experimental-theoretical investigation on interaction of vacuum-ultraviolet radiation with trimethylphosphate (TMP) molecule (C(3)H(9)O(4)P) in gas phase. This species together with tetrahydrofuran (THF) are model compounds of deoxyribose nucleic acids (DNA)/ribose nucleic acids (RNA) backbone. Absolute photoabsorption cross sections (σ(a)) and ionization yields (η) are measured using the double-ion-chamber technique in the 11.0-21.45 eV energy range. Photoionization (σ(i)) and neutral-decay (σ(n)) cross sections in absolute scale are also derived. Moreover, theoretical photoabsorption cross sections are calculated using the time-dependent density functional theory from the excitation threshold up to 16 eV. Good agreement between the present calculated and experimental photoabsorption cross sections in the 11.0-14.5 eV range is encouraging. Also, the present measured data of σ(a) and σ(i) for TMP are about 1.3 and 1.5 times of those of THF, respectively. Thus, the experimental evidences that the majority of strand breaks being located at sugar rings in the irradiated DNA/RNA backbone moiety may be induced by a possible migration of the hole, initially created at phosphate group, to the linked sugar groups. Finally, absolute partial photoionization cross sections are derived from the experimental time-of-flight mass spectra.