Photon Absorption Cross Section Research Articles

The energy-weighted sum rule and the nuclear radius

The energy-weighted integrated cross-section for photon absorption --known as sum rule \( \sigma_{-1}\) -- is under certain conditions proportional to the mean square nuclear radius (Levinger, Bethe (Phys. Rev. 78, 115 (1950))). Due to the energy weight factor the low-energy absorption components are emphasized and the dipole transitions in the region of giant resonances contribute enhanced at \( \sigma_{-1}\) . Thus, the cross-section of the full interaction can be replaced in good approximation by the dipole cross-section. Under these aspects, we have calculated \( \sigma_{-1}\) and the radii of various gg-nuclei. For our purpose, we have chosen a simple shell model where the integrals can be solved analytically, and the contributions of uncorrelated functions and correlation corrections can be shown explicitly. The mean square radius as a function of \( \sigma_{-1}\) differs by a factor of 1.5/0.87 from the previous result of Levinger and Kent (Phys. Rev. 95, 418 (1954)) without correlation corrections. Plotting the function of the correlation corrections \( g(A)\) and the uncorrelated function \( f(A)\) as a ratio it shows that \( g(A)/f(A)\) tends towards a limit. Finally, our results for the radii of gg-nuclei are in good agreement with recent experiments (I. Angeli, K.P. Marinova, At. Data Nucl. Data Tables 99, 69 (2013)).

Enhanced two photon absorption cross section and optical nonlinearity of a quasi-octupolar molecule

Abstract Two photon absorption (2PA) cross sections of two quasi-octupolar molecules ( E , E , E )-2,4,6-tris [2-(4- N , N -diphenylaminophenyl)vinyl]pyridine (DPATSP) and (2,4,6-tris(( E )-4-(diphenylamino)styryl)-1-methylpyridine-1-ium iodide, DPATSP-Me) have been estimated. It has been found that by introducing the pyridinium ion, the 2PA cross section of DPATSP-Me increases with respect to the parent molecule, DPATSP. Z-scan experiments on the two samples reveal that DPATSP-Me is a better candidate for optical limiting applications.

The effect of heavy atom to two photon absorption properties and intersystem crossing mechanism in aza-boron-dipyrromethene compounds

New aza-boron-dipyrromethene compounds containing bromine atoms at various positions were designed and synthesized to enhance the triplet state population and two photon absorption properties for applications such as two-photon photodynamic therapy, triplet–triplet annihilation up-conversion. Steady state fluorescence and ultrafast pump probe spectroscopy techniques revealed that only 2, 6 positions of aza-boron-dipyrromethene core contribute to triplet state population significantly. Density function theory calculations showed that when bromine atoms introduced to 2, 6 position of aza-boron-dipyrromethene core, singlet and triplet energy levels get closer therefore probability of intersystem crossing increases. Z-scan experiments at 800 nm wavelengths revealed considerably large (610 GM) two photon absorption cross section value with respect to literature for compounds showing intersystem crossing mechanism. The efficient intersystem crossing and enhanced two-photon absorption properties make the investigated aza-boron-dipyrromethene compounds good candidates for two-photon photodynamic therapy application.

Synthesis and optical properties of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores

Cationic cyclopentadienyl iron complexes of arenes are applied in photopolymerization and photocatalysis because of their good photophysical and photochemical properties. In this study, a series of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores (Aky-Fc) was obtained via nucleophilic substitution and Suzuki coupling reactions. The linear and nonlinear optical properties of the obtained molecules were tuned by phenylethynyl linkages. The UV–Vis absorption spectra showed that increasing the conjugation by substituting phenylacetylene spacer resulted in a red shift in the absorption bands and much stronger absorption in Aky-Fc than in (η6-cumene) (η5-cyclopentadienyl) iron hexafluorophosphate (I-261). With the single-beam Z-scan technique, the nonlinear absorption of Aky-Fc showed that Aky-Fc (8), (9), and (10) had good nonlinear optical ability, and the two photon absorption (TPA) cross section σ was approximately 10times that of I-261.

Luminance Conversion Property of Er and Yb Doped KZnF3Nanocrystal Synthesized by Hydrothermal Method

In order to make full use of exposure energy, one feasible way is to modify the luminance of crystal by rare earth doping technique. KZnF3:Er3+and KZnF3:Er3+/Yb3+nanocrystals of uniform cuboid perovskite type morphology, with average diameter of 130 nm, has been synthesized by hydrothermal method. When Yb3+ions were codoped with Er3+, absorption peak at 970 nm has been heightened and widened, and the photon absorption cross section increased. The common xenon lamp exposure cannot initiate obvious nonlinear phenomenon of the doped Er3+and Yb3+, and exposing at 245 nm only excites the fluorescence around 395 nm. Contrarily, under high power IR exposure at 980 nm, obvious upconversion photoluminescence (PL) has been observed due to the two-photon process. The PL mechanism of the doped Er3+ion in KZnF3:Er3+/Yb3+nanocrystals is confirmed. Furthermore, Yb3+codoped as sensitizer has modified the PL intensity of Er3+from green light range to red range, and the primary channel is changed from4S3/2(Er3+) →4I15/2(Er3+) of only Er3+doped KZnF3nanocrystal to4F9/2(Er3+) →4I15/2(Er3+) of Er3+/Yb3+codoped sample. With exposure energy increasing, such primary transition channel after two-photon excitation is unchanged.

Abstract LB-9: Light-controllable nano-drug delivery system with deep tissue penetrating ability for cancer therapy with two-photon-triggered nanoimpellers

Abstract Controllable drug delivery is urgently pursued for cancer therapy, because conventional chemotherapy is associated with serious toxic side effects. Precisely controlled external stimuli-activated nanoparticles are promising, as selective activation of the system takes place only upon stimulation of trigger signals and only in the area of interest. Silica nanoparticles have a number of advantages such as well established synthesis methods, chemical and thermal stability, large drug loading capacity, and the ease to carry out various surface modifications. We previously showed that our mesoporous silica nanoparticle-based nanoimpellers are effective for photo-activated drug delivery. However, like other light activating nanoparticles, our nanoimpeller also employed UV/Vis light, thus limiting its medical applications due to its short wavelength and inability for deep tissue penetration. Here we report our new generation of nanoimpellers functionalized with two-photon fluorophore that has a high two photon absorption cross-section, suitable for fluorescence resonance energy transfer (FRET) to photoisomerize azobenzene moieties in the NIR region. The azobenzene residing in the porous framework allows physical entrapment of the anticancer drug camptothecin, which is then propelled out of the pores by two-photon-triggered photoisomerization, resulting in on-demand intracellular drug release. Intracellular release of molecules is dependent on light excitation powers and wavelengths, and the anticancer drug delivery inside of cells can be regulated with light excitation. TPE fluorescence imaging was performed to demonstrate the cellular uptake of the nanoimpellers. Nanoimpeller with a high energy transfer quantum yield from the fluorophore to the azobenzene moiety was able to induce cancer cell death under these TPE conditions and did not show toxicity to control cells that were shielded from light. In a similar but different design, we also synthesized nanoparticles that have nanovalves placed at the pore openings. These results suggest that our newly synthesized two-photon-activated nanoimpellers could be useful for cancer therapy because of deep tissue penetrating ability and controllability. Actual application of such light-triggered delivery system in animal models remains to be proven, but we believe this two-photon light-activated mesoporous silica nanoparticles have a broad application prospects for biomedicine. Citation Format: Jie lu, Jonas Croissant, Jean-Olivier Jean-Olivier Durand, Tania Guardado-Alvarez, Jeffrey I. Zink, Fuyuhiko Tamanoi. Light-controllable nano-drug delivery system with deep tissue penetrating ability for cancer therapy with two-photon-triggered nanoimpellers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-9. doi:10.1158/1538-7445.AM2014-LB-9

Effects of pyrene on the photophysical and two-photon absorption-based nonlinear optical properties of indium(III) phthalocyanines

Photophysical and two-photon-dependent nonlinear absorption properties of two chloroindium(III) phthalocyanines bearing pyrene units have been investigated. The tetra- (3) and the tri- (4) pyrene-substituted phthalocyanines exhibit strong triplet absorption with high triplet yields () of 0.79 and 0.83, respectively. The measured nonlinear optical data, such as the two photon absorption cross-sections, the third- and second-order nonlinearities were found to be comparable with those of literature, thus, making the compounds promising candidates for a broad range of nonlinear optical applications.

Design of luminescent ZnSalen for molecular imaging

Design of luminescent metal complexes for imaging molecular events occurred intracellular is of importance to expand the scope of application of inorganic complexes in molecular imaging. In this review, we focused on the design of new transition metal complexes as biological optical probes and demonstrated their applications in seeing particular molecular events. ZnSalens (Salen = 2,3-bis[(4-dialkylamino-2-hydroxybenzy-lidene) amino] but-2-enedini-trile) luminescent metal probes exhibit high fluorescence with nonlinear optical properties as well as large two photon absorption cross-section. It is consisted with an electron-donor (D)/electron-acceptor (A) pair with intramolecular charge transfer (ICT), which renders ZnSalen a core structure for designing photoactivatable fluorophores. Combined with other attractive features in a biological context such as good membrane permeability and low cytotoxicity, further design and application of ZnSalens as a novel type of photoactivable fluorophore is promising in super resolution microscopes such as PALM, STED and STORM.

The new frozen spin target at MAMI

The new frozen spin polarized target for experiments at the polarized beam of the real photon facility A2 of the MAMI accelerator is described. The A2-collaboration at the Mainz Microtron MAMI is measuring photon absorption cross section using circularly and linearly polarized photons up to the energy of 1.5 GeV. The photons are produced in the’ Bremsstrahlungs’ process. In the years 2005/2006 the Crystal Ball detector with its unique capability to cope with multi photon final states was set up in Mainz. Since 2010 the experimental apparatus has been completed by a polarized target. The horizontal dilution refrigerator of the Frozen-Spin Target has been constructed and is operated in close cooperation with the Joint Institute for Nuclear Research in Dubna, Russia. The system offers the opportunity to provide longitudinally and transversely polarized protons and deuteron. In this paper the operation experience of this new Frozen-Spin Target and first results from the runs in 2010 and 2011 are presented.

Frequency dependence of electron dynamics during femtosecond laser resonant photoionization of Li4 cluster

This study investigates the resonant effects on nonlinear photoionization of Li4 cluster under femtosecond laser irradiation. The real-time and real-space time-dependent density functional theory is applied to describe the optical linear response and nonlinear electron dynamics during the laser-material interactions. The calculations describe well the behaviors of the ionization process for both the off resonance and on resonance cases. For given laser intensities, the frequency dependence of electron ionization and energy absorption on multiphoton and/or tunnel ionization mechanisms is investigated. Theoretical results show that (1) the off resonance behaves as a classical oscillator whereas resonance leads to an internal excitation with subsequent emission of electrons after the laser termination; (2) when multiphoton ionization dominates, the frequency dependence of emitted electrons and absorbed energy coincides with trend of the spectral cross section for photon absorption; (3) while when tunnel ionization becomes significant, the aforementioned correlation gradually disappears, and the enhancement of resonant effect on photoionization is not manifest.

Investigation of third-order nonlinear and optical power limiting properties of terphenyl derivatives

Abstract A series of new chalcones containing terphenyl as a core and with different functional groups has been successfully synthesized by Claisen–Schmidt condensation method in search of new nonlinear optical (NLO) materials. Molecular structural characterization for the compounds was achieved by FTIR and single crystal X-ray diffraction. The third-order NLO absorption and refraction coefficients were simultaneously determined by Z-scan technique. The measurements were performed at 532 nm with 7 ns laser pulses using a Nd:YAG laser in solution form. The Z-scan experiments reveal that the compounds exhibit strong nonlinear refraction coefficient of the order 10 –11 esu and the molecular two photon absorption cross section is 10 –46 cm 4 s/photon. The results also show that the structures of the compounds have great impact on NLO properties. The compounds show optical power limiting behavior due to two-photon absorption (TPA).

Exact Analytical Formulism for Erbium Doped Fiber Lasers

An exact analytical formulism obtained directly by solving a system of rate and propagation equations in the presence of pump excited-state absorption is presented on the basis of four-band transition scheme in radially symmetric and longitudinally uniform monomode erbium doped silica fiber lasers. The exact analytical expressions are determined for overall gain, small-signal gain, pump intensity threshold, lasing threshold condition, and optimal fiber length in terms of alleviative measurable quantities of photon intensities, transition rates, absorption and emission cross sections, and reflectivity of mirrors. Mutatis mutandis, the formulas bear a verisimilitude to analytical expressions appearing in the literature for these parameters.

Carbon disulfide as a dopant in photon‐induced chemical ionization mass spectrometry

The addition of a dopant to an Atmospheric Pressure PhotoIonization (APPI) source of a mass spectrometer has been shown to enhance the degree of analyte ionization. A series of different dopants has been successfully utilized; however, there has been very little published on the characteristics of a good dopant. We have proposed carbon disulfide (CS2) as a novel new dopant based on its absorption cross-section for the VUV photon's energy used and its unique gas-phase ion chemistry, notably the fact that it does not contain a proton. The ability of CS2 to enhance the ionization effectiveness of APPI was tested by using a group of compounds that have different proton affinities (PAs) and electron affinities (EAs). These results were compared to results obtained using the commonly used dopants, toluene and anisole. Particular attention was paid to the formation of [M](+) ions relative to [M+H](+) ions. Mass spectra were collected using a Waters Quattro Premier liquid chromatography/tandem mass spectrometry (LC/MS/MS) system equipped with a commercial Photomate™ photoionization source. The results show that CS2 increases the ionization efficiency of most of the analytes studied in this work comparably to toluene and anisole. CS2 promotes both ionization routes of [M](+) and [M+H](+). In addition, due to the higher ionization energy (IE) of CS2 (10.01) compared to the IEs of toluene (8.83) and anisole (8.20), CS2 can enhance the ionization efficiency of analytes that cannot be enhanced with toluene and anisole. We have determined that CS2 is a viable dopant for use in APPI sources. For some analytes, significant [M+H](+) ion signals are observed; therefore, the donated proton must come from either water clusters or solvents. In addition, CS2 promotes the ionization of analytes with low PAs and higher IEs than that of toluene and anisole.

The effect of charge transfer on the ultrafast and two-photon absorption properties of newly synthesized boron-dipyrromethene compounds

New BODIPY compounds containing nitro, diphenylamine and triphenylamine groups were designed and synthesized to enhance two photon absorption properties at NIR region by increasing charge transfer mechanism. Charge transfer mechanisms were investigated with linear absorption, fluorescence and ultrafast pump-probe absorption spectra. Solvents with various polarities were used to better understand the charge transfer properties of investigated compounds. Open aperture Z-scan experiments showed that charge transfer enhanced to two photon absorption properties. Two photon absorption cross section value was measured as 220 GM at 800 nm wavelength for the 3TFABDP compound. This value at 800 nm wavelength is considerably high compared to similar BODIPY compounds in literature.

Synthesis, characterization and evaluation of the photophysical and nonlinear optical behaviour of novel 4-substituted arylidene-2-[5-(2,6-dichlorophenyl)-3-methyl-1,2-oxazol-4-yl]-1,3-oxazol-5-ones

Five new 4-substituted arylidene-2-[5-(2,6-dichlorophenyl)-3-methyl-1,2-oxazol-4-yl]-1,3-oxazol-5-ones have been designed and synthesized in order to study their third-order nonlinear optical properties. These novel compounds were characterized by advanced spectroscopic techniques (IR, 1H, 13C NMR, ESI-MS spectroscopy and elemental analyses). In addition, the evaluation of absorption and emission wavelengths of the new 5-oxazolone derivatives was carried out in seven different solvents of varying polarity, which showed intense absorption maxima at 350–480 nm and emission maxima at 390–535 nm respectively. The third-order nonlinear optical properties of the target molecules have been investigated in N,N-dimethylformamide using a single beam Z-scan technique with nanosecond laser pulses at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, magnitude of third-order susceptibility and molecular two photon absorption cross-sections have been determined. All of the compounds showed excellent optical limiting behaviour at 532 nm, with the best optical limiting behaviour observed with strong electron donor [dimethyl and N,N-diethyl amino] substituents.

Optical absorption of Mg-doped layers and InGaN quantum wells on c-plane and semipolar GaN structures

We studied optical absorption of Mg-doped AlInGaN layers using excitation-position dependent and polarization resolved photoluminescence from the slab-waveguide edge of a laser structure. The major absorption in the Mg-doped layers was found only when p-doping is activated. It increases with the removal of residual hydrogen, which in case of Mg doping is a p-type passivation impurity, and reversibly disappears after passivation by hydrogen. This absorption is weakly wavelength and temperature dependent, and isotropic. This can be attributed to acceptor-bound hole absorption, because those holes concentration is nearly equal to that of activated acceptors and weakly temperature dependent (unlike the free hole concentration, which is much lower and is an exponential function of temperature due to high ionization energy). The cross section of photon absorption on such activated acceptor was quantified to be in the order of 10−17 cm−2. The absorption cross section of free electrons was found to be at least one order of magnitude lower and below detection limit. The same technique was used to experimentally quantify band structure polarization components along basis directions for green InGaN quantum wells (QWs) grown on c- and semipolar planes. The A1 and B1 valence subbands of c-plane QW were found to comprise mostly |X⟩ and |Y⟩ states. There was rather minor amount of |Z⟩ states with average square fraction of only 0.02. In (20-21) plane, due to small band anticrossing near gamma-point, we observed highly polarized absorption edges of A1- and B1-subbands consisting mainly of |Y⟩ and |X⟩ states, respectively, and found their energy splitting to be ∼40 meV. For (11-22) plane with smaller band splitting and polarization, we observed polarization switching with indium (In) concentration greater than 30% in the QW (or photon energy less than 2.3 eV). We confirmed our study of valence band structures by optical gain measurements.

Wavelength-Resolved UV Photoelectric Charging Dynamics of Nanoparticles: Comparison of Spheres and Aggregates

The objective of this work is to understand the charging dynamics of metal nanoparticles under wavelength-selected UV irradiation, with a particular focus on the effect of particle structure on the quantum yield. We employed an ion mobility analysis technique to measure the size-resolved single charging efficiency of structure-controlled silver nanoparticles (spheres vs. aggregates) in the mobility diameter (D m) range of 10 ∼ 100 nm. We found that the measured particle charging efficiency follows D 2 m dependence for both spherical and aggregate particles. Based on the measured charging efficiency and calculated particle photon absorption cross section, we are also able to determine the mobility size dependence of photoelectric quantum yield for both spheres and aggregates. The quantum yield of spheres is a constant for larger particles (50 nm or larger) but significantly enhanced as particle size decreases. The quantum yield of aggregates is shown to be particle structure dependent and does not behave a...

Enhancement of two photon absorption properties by charge transfer in newly synthesized aza-boron-dipyrromethene compounds containing triphenylamine, 4-ethynyl-N,N-dimethylaniline and methoxy moieties

Abstract The effects of substitution and charge transfer on linear and nonlinear optical absorption (especially two photon absorption) properties of aza-BODIPY containing triphenylamine, 4-ethynyl-N,N-dimethylaniline and methoxy moieties were investigated by ultrafast pump probe spectroscopy technique. Fluorescence and ultrafast pump probe spectroscopy experiments revealed that aza-BODIPY compounds with good electron donating moieties (triphenylamine and 4-ethynyl-N,N-dimethylaniline moieties) have charge transfer from electron donating parts of the molecules to aza-BODIPY core. The two photon absorption cross sections increase with the electron donating strength. Maximum two photon absorption cross section is obtained as 126 GM at telecommunication wavelength (1310 nm) for aza-BODIPY compound containing triphenylamine, 4-ethynyl-N,N-dimethylaniline. Our results indicate that charge transfer enhances two photon absorption properties.

Synthesis, structure, and one- and two-photon absorption properties of N-substituted 3,5-bisarylidenepropenpiperidin-4-ones

A series of 3,5-bisarylidenepropenpiperidin-4-one compounds with a D–π–A–π–D structure, containing donors (R1=NEt2, NMe2) and terminal groups at the central nitrogen ring atom (R2=H, Me, Et, P(O)(OEt)2) was synthesized with the goal of improving one- and two-photon absorption properties of the earlier designed compounds, which potential activity as photosensitizers was demonstrated with appeal of biological and spectroscopic data. Several of the compounds studied have a two photon absorption cross section approximately six times larger than previously measured for 3,5-bisarylidenemethylenpiperidin-4-ones with short alkene chains. Spectral data are discussed in connection with structural characteristics of studied materials.

Analytical absorption cross section for photon by helium 23s metastable state

We calculate the absorption cross section for photons by the helium 23s metastable state using the quantum–classical approximation for the total photo cross section of many-electron atoms. We note that for the 1s2s configuration of the helium 23S metastable state the photons can be absorbed by either a 1s or 2s electron. The absorption cross section of photons by the 1s and 2s electrons are predominant at high and low energies, respectively. The calculated absorption cross section for a 1s electron agrees perfectly with theoretical results. However, those of the 2s electron do not agree perfectly with experimental and theoretical results, because of the dip associated with the Cooper pair minimum at the zero crossing of the 2s hydrogenic spatial wave function. We have included in the analytical calculation, the second-order term of the Baker–Hausdorff expansion and observed a great reduction in the dip associated with the Cooper pair minimum, at low photon energy.