Photon Absorption Cross Section Research Articles

High-intensity pulsed-light cultivation of unicellular algae: Photosynthesis continues in the dark

Experiments have shown that photon exploitation efficiency in unicellular algal biomass production under a pulsed-light regime with a high-photon flux is higher than the efficiency under continuous illumination with the same flux. This observation has been explained theoretically to be a consequence of the improved efficiency of exploitation of photons by Photosystem II (PS II) thanks to the combined effect of photon-absorption statistics, a rate-limiting time scale and the size of the PQ pool.Exploiting the same ideas, it is shown in this paper that, under a pulsed-light regime, there is a pulse-time length, for which the average exploitation efficiency of PS II absorbed photons is maximal. Under ideal conditions, this maximum is close to 100%. The optimal pulse-time length is roughly proportional to the size of the PQ pool, NPQ. This is clearly seen for τ (the average time gap between consecutive photons absorbed by the PS II-Chlorophyll antenna) of the order of 1 ms or less (corresponding to a high photon flux and/or a large photon absorption cross-section area of the antenna) and for small NPQ. The width of the plot of efficiency vs. pulse length around the optimum is then small and the optimal pulse length is well defined. As τ is increased beyond 1 or NPQ becomes large, the width grows, allowing for a broad choice of pulse lengths, for which efficiency is very close to the maximum.These observations open the door to future designs of highly productive bioreactors.

Radiation attenuation of fly ash and rice husk ash-based geopolymers as cement replacement in concrete for shielding applications

Due to the economic and environmental cost of producing cement for concrete, research into the use of alternative materials such as geopolymers for the partial replacement of cement has become popular. In an attempt to understand the effect of such replacement on the shielding behavior of concrete, this study evaluated and analyzed the gamma-ray interaction parameters of fly ash- and rice husk ash-based geopolymers (G-RHA-F1, G-RHA-F2, G-RHA-F3, and G-RHA-F4). The mass attenuation coefficient (μρ), mass energy absorption coefficient (μenρ), effective atomic number (Zeff), specific gamma-ray dose constant (Г), dose rate (Dr), and photon buildup factors (BFs) were computed for photon energies within 15,000 eV and 15,000 keV. The evaluated parameters showed differences in value for the materials. For G-RHA-F1, G-RHA-F2, G-RHA-F3, and G-RHA-F4, μρ values are within the range 0.0208–6.5169 cm2/g, 0.0208–6.3631 cm2/g, 0.0209–6.70611 cm2/g, and 0.0208–6.2149 cm2/g, respectively. The corresponding ranges of are 0.0155–5.9433 cm2/g, 0.0155–5.7934 cm2/g, 0.0156–6.4016 cm2/g, and 0.0155–5.6775 cm2/g, accordingly. Fly ash slightly improved the gamma photon absorption capacity of the geopolymers, especially at the low energies. The investigated geopolymers have relatively higher photon absorption cross-sections relative to some existing polymers and shielding glasses. They could therefore be used to construct effective concrete shields.

Synthesis of Oxazolones with Extended Conjugation and Evaluation of their Linear and Nonlinear Optical Photochemistry

AbstractOxazolones or azlactones are small heterocyclic systems that can be easily functionalized with a double bond directly attached to their structure. In addition, they can be substituted on the opposite side of the heterocycle with styrenyl groups to extend their conjugation. This allows for versatile tuning of their linear and non‐linear optical properties. In this work, eight doubly substituted oxazolones including different push‐pull or pull‐pull designs were synthesized, and their linear and non‐linear photophysical properties were studied. As we show, the two‐photon activity of these systems is dependent on the donor‐acceptor pattern, where a methoxy substitution on the styrene end of the molecule and an acetyl group on the other end shows two‐photon Z‐E conversion properties with an important two photon absorption cross section of 308 GM. Most oxazolones shown in this study undergo picosecond relaxation to the electronic ground state, releasing the biphotonic energy to their surrounding environment. The results obtained in this work are indicative of potential applications of these molecules in schemes where high spatial patterning or thermalization is required.

Manipulation of Giant Multipole Resonances via Vortex γ Photons.

Traditional photonuclear reactions primarily excite giant dipole resonances, making the measurement of isovector giant resonances with higher multipolarities a great challenge. In this Letter, the manipulation of collective excitations of different multipole transitions in even-even nuclei via vortex γ photons is investigated. We develop the calculation method for photonuclear cross sections induced by the vortex γ photon beam using the fully self-consistent random-phase approximation plus particle-vibration coupling (RPA+PVC) model based on Skyrme density functional. We find that the electromagnetic transitions with multipolarity J<|m_{γ}| are forbidden for vortex γ photons due to the angular momentum conservation, with m_{γ} being the projection of total angular momentum of γ photon on its propagation direction. For instance, this allows for probing the isovector giant quadrupole resonance without interference from dipole transitions using vortex γ photons with m_{γ}=2. Furthermore, the electromagnetic transition with J=|m_{γ}|+1 vanishes at a specific polar angle. Therefore, the giant resonances with specific multipolarity can be extracted via vortex γ photons. Moreover, the vortex properties of γ photons can be meticulously diagnosed by measuring the nuclear photon-absorption cross section. Our method opens new avenues for photonuclear excitations, generation of coherent γ photon laser and precise detection of vortex particles, and consequently, has significant impact on nuclear physics, nuclear astrophysics and strong laser physics.

Measurement of the photoabsorption cross section of 24Mg.

Accurate nuclear data is a key factor in determining the suitability and reliability of many theoretical nuclear models and large-scale calculations. One of the main ingredients of these calculations is how nuclei respond to an electromagnetic field. The excitation of the isovector giant dipole resonance (GDR) is of particular importance in both nuclear structure studies as well as being the main mode of interaction of ultra-high-energy cosmic rays with the extra-galactic medium. This study investigates the photoabsorption cross section in the region of the GDR in 24Mg through the use of proton inelastic scattering and the equivalent virtual photon method. The K600 spectrometer at the iThemba LABS facility was used to obtain high resolution, low background 24Mg(p,p’)24Mg* inelastic scattering data. The virtual photon absorption method is described and the result of applying the method is presented and compared to a previous real photon absorption cross section.

A compendium of photon emission rates, absorption cross sections and scattering cross sections

We provide a compendium of the quantum mechanical equations for photon emission rates, photon absorption cross sections, and photon scattering cross sections. For each case, the different equations that apply for discrete or continuous electron states of the emitting, absorbing, or scattering material are given.

The Rydberg 3p multiplet structure of the fenchone C band absorption.

The vibrationally structured 3pz Rydberg excitation is identified and assigned in the VUV absorption spectrum of fenchone with an origin at 6.31 eV, below the prominent 6.4 eV C̃ (nominally 3p) band onset. This feature cannot, however, be observed in (2+1) REMPI spectra, as its relative excitation cross-section is much reduced in a two-photon transition. The 3py and 3px excitation thresholds, found to differ by only 10-30 meV, lie around 6.4 eV corresponding to the first intense C̃ band peak in both VUV and REMPI spectra. Calculations of vertical and adiabatic Rydberg excitation energies, photon absorption cross-sections, and vibrational profiles are used to support these interpretations.

(Digital Presentation) Fabrication of Monolayer-Protected Gold Cluster Thin Films: Electrochemical and Optical Properties

Quantum-sized monolayer-protected gold clusters have captivated the imagination of scientists over the last two decades and show exciting optical, electrochemical and catalytic properties when compared to larger-sized plasmonic gold nanoparticles, making them useful for myriad new applications in photonics, catalysis and sensors. One interesting property is the photoluminescence (PL) of gold clusters making them suitable as biological imaging labels. However, the low PL Quantum Yields (QY) are a concern for these clusters and research is focused on improving the PL QYs. One strategy, our research group has worked on is the shell-gold rigidification via the use of surfactants and proteins. Shell ligand rigidification was achieved by ion pairing with bulky tertiary alkyl ammonium groups and aromatic chromophores. Another strategy to reduce the non-radiative deactivation pathways is by making the gold cluster thin films. In a recent study, it was shown that solid state films of clusters not only have manifold increase in PL quantum yield but also their luminescent lifetimes and two photon absorption cross-sections are greatly enhanced in comparison to their solution analogues. Researchers have worked on various strategies to make gold cluster thin films for device applications. One problem with thin films of gold clusters is that the clusters lose their interesting optical and electrochemical properties that were observed in solution phase. For making the clusters useful by enhancing PL for photonic device applications, it is important for the clusters to retain their properties in solid state, which is the main objective of the study carried out here. One problem is that drying intrinsic gold clusters results in crystallization whose optical properties are difficult to characterize. In this study, we have used Nafion and polyvinylpyrrolidone (PVP) to make thin films of water-soluble glutathione-protected gold clusters. Water soluble cluster Au22(SG)18 with reported PLQY of 8% were synthesized and characterized by UV-VIS absorption and PL measurements and thin films of these clusters were made using water soluble PVP and Nafion polymers via drop casting. Enhanced PL and electrochemical properties were observed for clusters in solid state. Similarly, non-polar gold cluster films are fabricated with Polystyrene and optical absorption and PL properties were retained in the solid state.Although drop casting with polymers was found to retain the optical properties, the uniformity of films is a problem. The uniformity of the film is dependent on solvent’s surface tension thus diminishing the quality of the film. Therefore, there is a need of depositing films of gold clusters in a controlled manner which governs their thickness and uniformity. Electropolymerization technique is known to make films during the polymerization of monomers possessing functional groups whose oxidation or reduction via anti-bonding or non-boding electrons on a heteroatom. In this study, we have used electropolymerization strategy to fabricate thin films of gold clusters on conducting substrates. The film is deposited at the working electrode during cyclic voltammetric (CV) sweep when passed through the required reduction or oxidation potential of the monomer under suitable conditions. This technique makes a uniform film throughout the exposed area of the working electrode active surface and the thickness of the film is often proportional to the number of sweep cycles employed. Therefore, introduction of gold clusters in this process with monomers which are previously known to bond with each other will incorporate clusters in the film during the polymerization process and will ease their film formation with uniform thickness. Amongst various size gold clusters, the one which shows good stability as a result of following the magic number series is Au25(SR)18 - . The stability of clustersis one of the important parameter required for practical applications. Aniline and other amine based monomers are used as precursors to make thin films of Au25 on conducting substrate such as Indium tin oxide. By solubilizing the gold clusters with the monomers they are deposited along with the polymers.

Entangled Photon Spectroscopy.

The enhanced interest in quantum-related phenomena has provided new opportunities for chemists to push the limits of detection and analysis of chemical processes. As some have called this the second quantum revolution, a time has come to apply the rules learned from previous research in quantum phenomena toward new methods and technologies important to chemists. While there has been great interest recently in quantum information science (QIS), the quest to understand how nonclassical states of light interact with matter has been ongoing for more than two decades. Our entry into this field started around this time with the use of materials to produce nonclassical states of light. Here, the process of multiphoton absorption led to photon-number squeezed states of light, where the photon statistics are sub-Poissonian. In addition to the great interest in generating squeezed states of light, there was also interest in the formation of entangled states of light. While much of the effort is still in foundational physics, there are numerous new avenues as to how quantum entanglement can be applied to spectroscopy, imaging, and sensing. These opportunities could have a large impact on the chemical community for a broad spectrum of applications.In this Account, we discuss the use of entangled (or quantum) light for spectroscopy as well as applications in microscopy and interferometry. The potential benefits of the use of quantum light are discussed in detail. From the first experiments in porphyrin dendrimer systems by Dr. Dong-Ik Lee in our group to the measurements of the entangled two photon absorption cross sections of biological systems such as flavoproteins, the usefulness of entangled light for spectroscopy has been illustrated. These early measurements led the way to more advanced measurements of the unique characteristics of both entangled light and the entangled photon absorption cross-section, which provides new control knobs for manipulating excited states in molecules.The first reports of fluorescence-induced entangled processes were in organic chromophores where the entangled photon cross-section was measured. These results would later have widespread impact in applications such as entangled two-photon microscopy. From our design, construction and implementation of a quantum entangled photon excited microscope, important imaging capabilities were achieved at an unprecedented low excitation intensity of 107 photons/s, which is 6 orders of magnitude lower than the excitation level for the classical two-photon image. New reports have also illustrated an advantage of nonclassical light in Raman imaging as well.From a standpoint of more precise measurements, the use of entangled photons in quantum interferometry may offer new opportunities for chemistry research. Experiments that combine molecular spectroscopy and quantum interferometry, by utilizing the correlations of entangled photons in a Hong-Ou-Mandel (HOM) interferometer, have been carried out. The initial experiment showed that the HOM signal is sensitive to the presence of a resonant organic sample placed in one arm of the interferometer. In addition, parameters such as the dephasing time have been obtained with the opportunity for even more advanced phenomenology in the future.

Two-Dimensional Cs2AgBiBr6/WS2 Heterostructure-Based Photodetector with Boosted Detectivity via Interfacial Engineering.

Two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers have been widely used for optoelectronic devices because of their ultrasensitivity to light detection acquired from their direct gap properties. However, the small cross-section of photon absorption in the atomically thin layer thickness significantly limits the generation of photocarriers, restricting their performance. Here, we integrate monolayer WS2 with 2D perovskites Cs2AgBiBr6, which serve as the light absorption layer, to greatly enhance the photosensitivity of WS2. The efficient charge transfer at the Cs2AgBiBr6/WS2 heterojunction is evidenced by the shortened photoluminescence (PL) decay time of Cs2AgBiBr6. Scanning photocurrent microscopy of Cs2AgBiBr6/WS2/graphene reveals that improved charge extraction from graphene leads to an enhanced photoresponse. The 2D Cs2AgBiBr6/WS2/graphene vertical heterostructure photodetector exhibits a high detectivity (D*) of 1.5 × 1013 Jones with a fast response time of 52.3 μs/53.6 μs and an on/off ratio of 1.02 × 104. It is worth noting that this 2D heterostructure photodetector can realize self-powered light detection behavior with an open-circuit voltage of ∼0.75 V. The results suggest that the 2D perovskites can effectively improve the TMDC layer-based photodetectors for low-power consumption photoelectrical applications.

Angle-resolved line profiles in the predissociation of D2 : A summation of Fano and Lorentzian profiles

Fano profiles usually refer to the line profiles due to the total photon absorption cross sections. In this work, we measured the angle-resolved line profiles of the $\mathrm{D}(2s,2p)$ fragments from the predissociation of ${\mathrm{D}}_{2}$ near the second threshold using the D-atom Rydberg tagging time-of-flight method. The line profiles of the fragments recoiling at the parallel and perpendicular directions to the polarization direction of the excitation laser were found to be significantly different from each other, as well as with the Fano profiles of total absorption cross sections. Based on the previous theoretical results, we found that the angle-resolved line profiles can be expressed as a summation of Fano and Lorentzian profiles. Using the formula and the previously determined parameters from the so-called \ensuremath{\beta} profiles, we calculated the angle-resolved line profiles, which are in good agreement with the experimental data. Anisotropy parameters arising from the interferences between the continuum and discrete states were found to play a role in the angle-resolved line profiles.

Triplet exciton dynamics of pure organics with halogen substitution boosted two photon absorption and room temperature phosphorescence: A theoretical perspective

Organic room temperature phosphorescence (RTP) molecules have shown promising applications in organic light emitting diodes and vivo imaging. Thus, triplet exciton dynamics in solid phase should be revealed and the molecule should possess large two photon absorption (TPA) cross sections under near-infrared excitation. The effects of halogen substitution and intermolecular interaction on RTP and TPA properties are studied at molecular level for a series of derivatives. Surrounding environment in solid phase is considered by combined quantum mechanics and molecular mechanics method. Intermolecular interactions are evaluated by the independent gradient model and calculated through the molecular force field energy decomposition method. Minimum energy crossing point, Huang-Rhys factor and reorganization energy are discussed, triplet exciton dynamics are investigated by thermal vibration correlation function method. Results indicate that the largest TPA cross sections are found for molecule in water. The halogen substitution can enlarge the proportion of (π, π*) and facilitate the intersystem crossing process. Restricted intramolecular rotation motions of dihedral angle in low frequency regions are found for Br-Np-Cz-BF2 in solid phase. While enhanced vibrations of bond length and bond angle in high frequency regions are detected for I-Np-Cz-BF2. Effects of halogen substitution and intermolecular interaction on triplet exciton dynamics are highlighted.

Using femtosecond laser pulses to study the nonlinear optical properties of rhodamine 6G dissolved in water

Using the Z- scan method, we studied the nonlinear absorption coefficient of rhodamine 6G dissolved in water. With laser pulses of 100 fs, the nonlinear absorption coefficient was measured at different excitation wavelengths and incident powers for both water and R6G. Water behavior showed saturable absorption (SA) at high power (>0.8 W) but at low laser power (<0.8 W) does not exhibit any nonlinearity whatever of the wavelength of excitation. At high laser power, the nonlinear absorption coefficient of the water increases as the wavelength decreases. A transition from saturable absorption to reverse saturable absorption (RSA) was observed when R6G was added to the water. In the case of R6G solution, the nonlinear absorption coefficient was found to be sensitive to both excitation wavelength and power. The two photon absorption cross-section was obtained from the nonlinear absorption coefficient of rhodamine 6G solution and was found to increase with increasing excitation wavelength while increasing with decreasing laser power. The nonlinear absorption coefficient β and nonlinear refractive index n2 of rhodamine 6G solution were found to be concentration dependent. Based on its RSA behaviour, the optical limiting of rhodamine 6G solution was measured and found to be concentration dependent. The higher concentration of rhodamine 6G solution has better optical limiting characteristics.

Great enhancement of two photon absorption cross section value by intramolecular charge transfer in newly synthesized triphenylamine-BODIPY derivative

Novel borondipyrromethene (BODIPY) compound without a −8 (meso) substituent containing triphenylamine moieties via Suzuki-Miyaura coupling was designed and synthesized to enhance two photon absorption (TPA) property. The effect of π-expanded triphenylamine moieties and absence of meso substitution in BODIPY core on charge transfer dynamics as well as two photon absorption properties were investigated by utilizing ultrafast transient absorption spectroscopy measurements and open aperture (OA) Z-scan experiments in the environment of both in solution and host poly (methyl methacrylate) (PMMA) polymer film. The BODIPY compound with triphenylamine moieties has intramolecular charge transfer characteristics from electron donating moieties to BODIPY core due to its strong electron donating property and long conjugation length. The BODIPY compound with triphenylamine moieties demonstrates higher TPA cross section compared to reference compound based on the OA Z-scan experiments attributed to the strong coupling between the highest occupied molecular orbitals of BODIPY and 4-N,N-diphenylaminobiphenyl moieties. TPA cross section values were found to be 58 GM and 688 GM at 800 nm wavelength for reference BODIPY (BDP-1) and BODIPY-triphenylamine (BDP-2) compounds, respectively. BODIPY-triphenylamine compound has one of the greatest TPCS value among of the studied BODIPY compounds in the literature and may be a good candidate for photodynamic therapy and bio-imaging applications due to the free heavy atom nature.

Modulated Luminescence of Lanthanide Materials by Local Surface Plasmon Resonance Effect.

Lanthanide materials have great applications in optical communication, biological fluorescence imaging, laser, and so on, due to their narrow emission bandwidths, large Stokes’ shifts, long emission lifetimes, and excellent photo-stability. However, the photon absorption cross-section of lanthanide ions is generally small, and the luminescence efficiency is relatively low. The effective improvement of the lanthanide-doped materials has been a challenge in the implementation of many applications. The local surface plasmon resonance (LSPR) effect of plasmonic nanoparticles (NPs) can improve the luminescence in different aspects: excitation enhancement induced by enhanced local field, emission enhancement induced by increased radiative decay, and quenching induced by increased non-radiative decay. In addition, plasmonic NPs can also regulate the energy transfer between two close lanthanide ions. In this review, the properties of the nanocomposite systems of lanthanide material and plasmonic NPs are presented, respectively. The mechanism of lanthanide materials regulated by plasmonic NPs and the scientific and technological discoveries of the luminescence technology are elaborated. Due to the large gap between the reported enhancement and the theoretical enhancement, some new strategies applied in lanthanide materials and related development in the plasmonic enhancing luminescence are presented.

Trans-cis Photoisomerization of a biomimetic cyclocurcumin analogue rationalized by molecular modelling.

Cyclocurcumin is a natural compound extracted from turmeric and showing, in addition to antiinfective, antibacterial, and intinflammatory capabilities, solvent-dependent phtoswitching ability. The solvent-dependent photochemistry of cyclocurcumin has been rationalized on the basis of a competition between π-π* and n-π* states. Recently we have reported the synthesis of a biomimetic analogue showing enhanced photochemical properties and in particular presenting photoswitching capacity in various media. In the present contribution we rely on the use of molecular modeling and simulation, incuding density functional and wavefunction based methods to explore the excited states potential energy surface landscape. We see that the addition of a carbon-carbon double bond to the core of the natural compounds favors the population of the π-π* state, whatever the choice of the solvent, and hence leads to photoisomerisation, with fluorescence reduced to only a minor channel, rationalizing the experimental observations. In addition, the two photon absorption cross section is also strongly increased compared to the parent compound, paving the way to the use in biologically oriented applications.

Investigation of the electric dipole (E1) excitations in $$^{\mathrm {181}}$$Ta nucleus

E1 transition properties such as the reduced transition probabilities, excitation energies and photon–absorption cross-sections have been theoretically investigated for $$^{\mathrm {181}}$$ Ta nucleus within the framework of Translational and Galileo Invariant-Quasiparticle Phonon Nuclear Model (TGI-QPNM). The model Hamiltonian includes the single-particle and the isovector dipole–dipole interaction terms along with the restoration forces. The strength of the isovector dipole–dipole interaction has been chosen to be $$\chi = 500/\hbox {A}^{\mathrm {5/3}} MeV \cdot fm^{-2}$$ . Theoretical calculations show that in addition to the M1 excitations, there is considerable amount of E1 transitions especially between 2.6–3 MeV, which gives remarkable contribution to the fragmentation in the low-energy region of the dipole spectrum. Thus, the agreement between theory and experiment in terms of the fragmentation increases. Furthermore, the photon–absorption cross-sections in the Pigmy Dipole Resonance (PDR) region below the neutron separation energy ( $$S_{n}$$ ) is compatible with experimental data.

Photophysical and nonlinear optical properties of the positional isomers of 4-(4-tertbutylphenoxy) substituted cobalt, nickel and copper phthalocyanines

This paper reports on the third order nonlinear optical properties of cobalt, nickel and tetrakis(4-terbutylphenoxy)phthalocyaninatocopper(II) isomers, using the Z-scan technique. Metal-free isomers were found to have high nonlinear absorption coefficient (β) values compared to the metalated isomers. Metal-free C2v isomer was found to have the highest β value of 1.52 × 10−10 mMW−1 in THF. All the metal-free and metal phthalocyanine isomers nonlinear properties were found to be dependent on the singlet state absorption. Imaginary second order nonlinear hyperpolarizability (Im[γ]), ground state cross section (σg), excited states cross sections (σs and σt) and two photon absorption (TPA) cross section (σTPA) values are reported in this work. The five-energy level model rate equations were used to model the nonlinear response and absorption cross sections.

Visible light responsive 2DCeO2-CdSQDs binary hybrid towards photocatalytic degradation of phenol

Environmental pollutions are now regarded as a major catastrophe for society, so the scientific community in search of efficient technology which can tackle this issue. Photocatalysis has emerged as one of the cost effective, clean and eco-friendly approach, which efficiently deals the various type of environmental pollutants. In this contest, different semiconductor materials have gained much more popularity. In this regard, we have modified 2D-CeO2 with CdSQDs with a simple deposition precipitation technique. As CdSQDs posses high cross-sections for multiple photon absorption and large oscillator strengths as compared with their bulk CdS counterparts makes it a suitable candidate for hybrid material with CeO2 which extends the spectral range of the absorption from UV to UV-visible range. Further, the formation of type-II heterostructure in between CdSQDs and 2D-CeO2 efficiently enhances the interfacial charge transfer and chemical stability. Structural, optical and morphological characterization of the fabricated samples were carried out by XRD, UV, PL and TEM analysis. The photocatalytic activity of the fabricated samples was tested towards phenol degradation where the degradation efficiency of hybrid CeO2NS-CdSQDs was found to be 71% in 2 h.

Acetylene bridged D-(π-A)2 type dyes containing benzophenone moieties: Photophysical properties, and the potential application as photoinitiators

Acetylene bridged acceptor-π-bridge-donor-π-bridge-acceptor (A-π-D-π-A) dyes (DBPs) based on benzophenone were designed and synthesized via Sonogashira coupling reaction utilizing carbazole/phenothiazine/triphenylamine as electron donating groups. The photophysical properties, photochemistry characteristics, as well as the two-photon absorption properties were studied. All dyes exhibited excellent intra-/intermolecular charge transfer properties upon excitation, and large two photon absorption cross sections in the wavelength range of 720~860 nm. Significant differences in fluorescence and photochemistry properties were found depending on the electron donating groups. The rigid carbazole favored hybridization of benzophenone like local excited state and intramolecular charge transfer excited state, which resulted in abnormal changes in fluorescence quantum yield, poor photostability, and good initiating ability both as Norrish Ⅱ initiator and as sensitizer for iodonium salt. However, the butterfly-shaped phenothiazine and propeller-shaped triphenylamine facilitated intramolecular charge transfer excited states, which resulted in typical positive solvatochromism effect, good photostabilities, and lacking of initiating ability as Norrish Ⅱ initiator.