Valence Band Electronic Structure of Azobenzene-Functionalized Gold Nanoparticles

Azobenzenes (Azo) represent a class of organic compounds composed of two phenyl rings linked by an N=N double bond that exhibit photoisomerization, i.e. change in conformation upon UV or visible light illumination. Photoisomerization in Azo is of high yield and reversible, which is why these molecules can act as molecular photoswitches in various biomedical and energy conversion applications. However, a broader application of Azo, particularly in biomedicine, requires lower energy of photoisomerization that falls further into visible or even NIR range. In our study, selected azobenzenes were conjugated to the surface of bare gold nanoparticles (Au NP) to obtain functional hybrid nanosystems in which photoisomerization of Azo can occur upon excitation of surface plasmon in Au NP. To understand the nature of the process, the valence band structure of Azo-functionalized Au NP was investigated by synchrotron radiation VUV aerosol photoemission spectroscopy. The results demonstrate that the overlap between the valence bands of Azo and Au NP is significant to allow for chare transfer process between the components in the nanosystem.XVI Photonics Workshop : Book of abstracts; March 12-15, 2023; Kopaonik, Serbi

Bare-carbon-ion-impact electron emission from adenine molecules: Differential and total cross-section measurements

Double-differential ionization cross sections (DDCS) for bare-carbon-ion-induced ionization of vapor-phase adenine molecules (C5H5N5) have been measured. The experiment has been performed using an electron spectroscopy technique. Electrons ejected from adenine were analyzed by a hemispherical electrostatic deflection analyzer over an energy range of 1-450eV for emission angles from 20 to 160. The single-differential cross section (SDCS) and total ionization cross section were also deduced. The experimental results have been compared with the continuum distorted wave-eikonal initial-state model calculation. We have observed a very good agreement between the theory and experiment. The angular distribution of the DDCS, SDCS and the asymmetry parameter for low-energy (Ee≤0.5 a.u.) electron display an oscillatory behavior which is in contrast to that observed in ion-atom collisions. A comparison is also made with available experimental cross-section results for uracil target colliding with the same velocity bare carbon ions and the scalability of ionization cross sections among these molecules is discussed.Fil: Bhattacharjee, Shamik. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Bagdia, Chandan. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chowdhury, Madhusree Roy. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Mandal, Anuvab. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Tribedi, Lokesh C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

M X-ray production cross-sections in

M X-ray yields of thin targets of 79Au and 83Bi in collisions with 50–300 keV protons have been measured. The production cross sections of Mζ[(M5–N3) + (M4–N2)], Mαβ[(M5–N6,7) + (M5–O3) + (M4–N6) + (M4–O2,3) + (M3–N2)], Mγ[(M3–N4,5) + (M2–N1)], Mm1[(M3–O1,4,5) + (M2–N4) + (M1–N2,3)] transitions and the total X-ray production cross-section are determined and compared to other available experimental values and also to those obtained from predictions of the PWBA and the ECPSSR models. The intensity ratios of the transitions are compared with the values calculated from the ECPSSR model. All existing experimental to theoretical ratios of the cross-sections as plotted as a function of the reduced velocity show a universal behaviour

Energy and angular distribution of electrons ejected from water by the impact of fast O8+ ion beams

Abstract: Double differential cross sections (DDCS) of electrons emitted from vapor water molecules (in vapor phase) by 2.0 MeV/u and 3.75 MeV/u bare oxygen ion impact have been measured by continuum electron spectroscopy technique. The ejected electrons were detected by an electrostatic hemispherical deflection analyzer over an energy range of 1–600 eV and emission angles from 20∘ to 160∘. The DDCS data has been compared with the continuum-distorted-wave-eikonal-initial state (CDW-EIS) approximation and a reasonable agreement was found with both version of the models i.e. post and prior version. By numerical integration of the DDCS data, the single differential cross section (SDCS) and total ionization cross section (TCS) were obtained. The obtained TCS results were compared with other available TCS results for water target within the same energy range. The total ionization cross sections values are seen to saturate as the projectile charge state (qp) increases, which is in contrast to the first-Born predicted qp 2 dependence. This is also in contrast to the prediction of the CDW-EIS models.Fil: Bhattacharjee, Shamik. Tata Institute of Fundamental Research; IndiaFil: Bagdia, Chandan. Tata Institute of Fundamental Research; IndiaFil: Chowdhury, Madhusree Roy. Tata Institute of Fundamental Research; IndiaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Tribedi, Lokesh C.. Tata Institute of Fundamental Research; Indi

Electron emission from bromouracil and uracil induced by protons and radiosensitization

Absolute double differential cross sections (DDCS) of electrons emitted from uracil and 5-bromouracil (BrU) in collisions with protons of energy 200 keV have been measured for various forward and backward emission angles over wide range of electron energies. The measured DDCS are compared with the continuum distorted wave-eikonal initial state (CDW-EIS) calculations. The optimized structure of the BrU was estimated along with the population analysis of all the occupied orbitals using a self-consistent field density. A comparison between the measured DDCS data for the two molecules show that the cross section of low energy electrons emitted from BrU is substantially larger than that for uracil. The BrU-to-uracil DDCS ratios obtained from the present measurements indicate an enhancement of the electron emission by a factor which is as large as 2.0 to 2.5. These electrons being the major agent for damaging the DNA/RNA of the malignant tissues, the present results are expected to provide an important input for the radiosensitization effect in hadron therapy. It is noteworthy to mention that the CDW-EIS calculations for Coulomb ionization cannot predict such enhancement. A large angular asymmetry is observed for uracil with a broad structure, which is absent in case of BrU

Coherent electron emission from O

Absolute double differential cross sections (DDCS) of secondary electrons emitted in ionization of O2 by fast electrons have been measured for different emission angles. Theoretical calculations of atomic DDCS were obtained using the first Born approximation with an asymptotic charge of ZT = 1. The measured molecular DDCS were divided by twice the theoretical atomic DDCS to detect the presence of interference effects which was the aim of the experiment. The experimental to theoretical DDCS ratios showed clear signature of first order interference oscillation for all emission angles. The ratios were fitted by a first order Cohen-Fano type model. The variation of the oscillation amplitudes as a function of the electron emission angle showed a parabolic behaviour which goes through a minimum at 90°. The single differential and total ionization cross sections have also been deduced, besides the KLL Auger cross sections. In order to make a comparative study, we have discussed these results along with our recent experimental data obtained for N2 molecule

Electron emission in ionization of adenine molecule induced by 5 MeV/u bare C ions

The double differential cross sections (DDCS) of electron emission in ionization of adenine molecule (C5H5N5) induced by 5 MeV/u bare C ions are measured using the electron spectroscopy technique. Emission of electrons from adenine is measured in the energy range from 20 eV to 460 eV and in the angular range from 20° to 160°. The single differential cross sections (SDCS) and total ionization cross section (TCS) are deduced from the e-DDCS. The experimental results are compared with the prior form of the continuum distorted wave- eikonal initial state (CDW-EIS) model prediction. Overall, a very good agreement between the theory and experiment is observed

Ionization of N2 in collisions with fast electrons: Evidence of an interference effect

p { margin-bottom: 2.47mm; line-height: 120%; }Absolutedouble differential cross sections (DDCS) of electron emission weremeasured for ionization of N2 by fast electrons with energy 7 keV. Measurements wereperformed for different electron emission angles and energies.Evidence of oscillation due to Young-type interference was observedin the DDCS ratios for all angles. The frequency for large backwardangle is found to be larger compared to that for small forward angle.Consequently, the forward-backward asymmetry parameter reveals theoscillatory structure even more clearly. The oscillations observedfor both experimental-to-heoretical DDCS ratios and forward-backwardasymmetry were well explained by the Cohen-Fano model of interferencein a molecular double slit. A periodic deviation of the Cohen-Fanomodel from the asymmetry parameter data reveals the presence of ahigher-frequency component.The first Born model was employed to explain the results of molecularnitrogen for which a complete-neglect-of-differential-overlapapproximation was used along with an effective atomic number.Fil: Roy Chowdhury, Madhusree. Tata Institute of Fundamental Research; IndiaFil: Stia, Carlos Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Tachino, Carmen Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fojon, Omar Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Tribedi, Lokesh C.. Tata Institute of Fundamental Research; Indi

Ionization of N2 in collisions with fast electrons: Evidence of an interference effect

p { margin-bottom: 2.47mm; line-height: 120%; }Absolutedouble differential cross sections (DDCS) of electron emission weremeasured for ionization of N2 by fast electrons with energy 7 keV. Measurements wereperformed for different electron emission angles and energies.Evidence of oscillation due to Young-type interference was observedin the DDCS ratios for all angles. The frequency for large backwardangle is found to be larger compared to that for small forward angle.Consequently, the forward-backward asymmetry parameter reveals theoscillatory structure even more clearly. The oscillations observedfor both experimental-to-heoretical DDCS ratios and forward-backwardasymmetry were well explained by the Cohen-Fano model of interferencein a molecular double slit. A periodic deviation of the Cohen-Fanomodel from the asymmetry parameter data reveals the presence of ahigher-frequency component.The first Born model was employed to explain the results of molecularnitrogen for which a complete-neglect-of-differential-overlapapproximation was used along with an effective atomic number.Fil: Roy Chowdhury, Madhusree. Tata Institute of Fundamental Research; IndiaFil: Stia, Carlos Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Tachino, Carmen Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fojon, Omar Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Tribedi, Lokesh C.. Tata Institute of Fundamental Research; Indi

Radiobiological effectiveness of iodouracil and the influence of atomic giant resonance

Hadron therapy combined with nanotechnology has been proposed as an elegant alternative for cancer treatment. Internal amplification of electron emission causing radiobiological effectiveness in nanoinserted biomolecules is of prime importance and has been measured here for the iodouracil molecule. Our experiment involves the measurement of angle and energy resolved double differential cross section (DDCS) of electron emission from iodouraciil and uracil (and also water) in collisions with fast C6+ ions. The electron emission from iodouracil is substantially enhanced over that from uracil or water. The enhancement is much larger than the state-of-the-art model for Coulomb ionization based on the continuum distorted wave-eikonal initial state (CDW-EIS) approximation. The electron sensitizing factor (˜2.4) is in excellent agreement with the strand-breaking sensitizing factor (˜2.0) for metal nanoparticle embedded in a DNA. The enhancement is explained in terms of collective excitation of strongly correlated 4d electrons, known as atomic giant dipole resonance (GDR) in I atoms. The GDR contribution to the enhancement is derived, which is in excellent agreement with recent theoretical prediction, thereby providing conclusive experimental evidence of the crucial role of collective excitation in radio sensitization.Fil: Mandal, Anuvab. International Centre of Theoretical Science. Tata Institute of Fundamental Research; EspañaFil: Chowdhury, Madhusree Roy. International Centre of Theoretical Science. Tata Institute of Fundamental Research; EspañaFil: Bagdia, Chandan. International Centre of Theoretical Science. Tata Institute of Fundamental Research; EspañaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Weck, Philippe F.. Sandia National Laboratories; Estados UnidosFil: Tribedi, Lokesh C.. International Centre of Theoretical Science. Tata Institute of Fundamental Research; Españ