Excited State Relaxation Dynamics Research Articles

Photodynamics of oxybenzone sunscreen: Nonadiabatic dynamics simulations.

Herein we have used combined static electronic structure calculations and "on-the-fly" global-switching trajectory surface-hopping dynamics simulations to explore the photochemical mechanism of oxybenzone sunscreen. We have first employed the multi-configurational CASSCF method to optimize minima, conical intersections, and minimum-energy reaction paths related to excited-state intramolecular proton transfer (ESIPT) and excited-state decays in the (1)ππ(∗), (1)nπ(∗), and S0 states (energies are refined at the higher MS-CASPT2 level). According to the mapped potential energy profiles, we have identified two ultrafast excited-state deactivation pathways for the initially populated (1)ππ(∗) system. The first is the diabatic ESIPT process along the (1)ππ(∗) potential energy profile. The generated (1)ππ(∗) keto species then decays to the S0 state via the keto (1)ππ(∗)/gs conical intersection. The second is internal conversion to the dark (1)nπ(∗) state near the (1)ππ(∗) /(1)nπ(∗) crossing point in the course of the diabatic (1)ππ(∗) ESIPT process. Our following dynamics simulations have shown that the ESIPT and (1)ππ(∗) → S0 internal conversion times are 104 and 286 fs, respectively. Finally, our present work demonstrates that in addition to the ESIPT process and the (1)ππ(∗) → S0 internal conversion in the keto region, the (1)ππ(∗) → (1)nπ(∗) internal conversion in the enol region plays as well an important role for the excited-state relaxation dynamics of oxybenzone.

Intramolecular Charge Transfer and Solvation of Photoactive Molecules with Conjugated Push–Pull Structures

A comparative investigation on the photophysical properties and solvation-related ICT dynamics of three push-pull compounds containing different donors including carbazole, triphenylamine and phenothiazine, was performed. The steady-state spectra and theoretical calculations show the charge transfers from the central donors to the acceptors at each side. The characterization of the extent of charge transfer was determined by various means, including estimation of the dipole moment, the electron density distribution of HOMO and LUMO, CDD and change in Gibb's free energy, which show the charge transfer strength to be in the order PDHP > BDHT > PDHC. This suggests that the electron-donating ability of the donor groups plays a crucial role in the charge transfer in these compounds. The TA data show the excited-state relaxation dynamics follow a sequential model: FC→ICT→ICT'→S0 , and are affected by the solvent polarity. The results presented here demonstrate that the compound with a higher degree of ICT characteristic interacts more strongly with stronger polar solvent molecules, which can accelerate the solvation and spectral evolution to lower energy levels. The A-π-D-π-A architectures with prominent ICT characteristics based on carbazole, triphenylamine and phenothiazine might be potential scaffolds for light-harvesting and photovoltaic devices. These results are of value for understanding structure-property relationships and the rational design of functional materials for photoelectric applications.

Femtosecond Pump-Probe Microspectroscopy of Single Perylene Nanoparticles.

We have developed a femtosecond pump-probe light scattering microspectroscopic system in which the output of a femtosecond Ti:sapphire oscillator (1 W, 82 MHz) was used as a light source; the pump light is the second harmonics (395 nm) of the laser output, and the probe light is a femtosecond white-light continuum (490-900 nm) generated with a photonic crystal fiber. Detection of the backscattered light from single nanoparticle on a glass substrate allowed us to obtain higher gain of the transient signals by ∼20 times in comparison with the conventional transmittance-mode experiment. This high-sensitivity of the backscattering detection makes it possible to examine ultrafast relaxation dynamics of excited states in organic nanoparticles, which, in general, are lower photodurability than the inorganic one. We applied the system to single nanocrystals of α-form perylene and then succeeded in direct observation of the excimer formation dynamics on a picosecond time scale. Single nanoparticle measurements for the perylene nanocrystals having a size range of 100 to 500 nm suggested that the excimer formation time became short from 2 ps to <0.3 ps for decreasing of the size.

Direct Observation of Cascade of Photoinduced Ultrafast Intramolecular Charge Transfer Dynamics in Diphenyl Acetylene Derivatives: Via Solvation and Intramolecular Relaxation.

Interaction of light with electron donor-acceptor π-conjugated systems leading to intramolecular charge transfer (ICT) plays an essential role in transformation of light energy. Here the cascade of photoinduced ICT processes is directly observed by investigating the excited state relaxation dynamics of cyano and mono/di methoxy substituted diphenyl acetylene derivatives using femtosecond pump-probe spectroscopy and nanosecond laser flash photolysis. The femtosecond transient absorption spectra of the chromophores upon ultrafast excitation reveal the dynamics of intermediates involved in transition from initially populated Frank-Condon state to local excited state (LE). It also provides the dynamic details of the transition from the LE to the charge transfer state yielding the formation of the radical ions. Finally, the charge transfer state decays to the triplet state by geminate charge recombination. The latter dynamics are observed in the nanosecond transient absorption spectra. It is found that excited state relaxation pathways are controlled by different stages of solvation and intramolecular relaxation depending on the solvent polarity. The twisted ICT state is more stabilized (978 ps) in acetonitrile than cyclohexane where major components of transient absorption originate from the S1 state.

Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy.

The excited state relaxation dynamics of the solvated electron in H2O and D2O are investigated using time-resolved photoelectron spectroscopy in a liquid microjet. The data show that the initial excited state decays on a time scale of 75 ± 12 fs in H2O and 102 ± 8 fs in D2O, followed by slower relaxation on time scales of 400 ± 70 fs and 390 ± 70 fs that are isotopically invariant within the precision of our measurements. Based on the time evolution of the transient signals, the faster and slower time constants are assigned to p → s internal conversion (IC) of the hydrated electron and relaxation on the ground electronic state, respectively. This assignment is consistent with the non-adiabatic mechanism for relaxation of the hydrated electron and yields an isotope effect of 1.4 ± 0.2 for IC of the hydrated electron.

Excited state relaxation dynamics and up-conversion phenomena in Gd3(Al,Ga)5O12 single crystals co-doped with erbium and ytterbium

Single crystals of Gd3(Al,Ga)5O12 (GAGG) doped with Er3+ or Yb3+ ions and co-doped with Er3+ and Yb3+ ions were grown successfully by the Czochralski technique. Their optical properties were investigated in detail. Rates of radiative transitions, branching ratio values and radiative lifetimes for excited multiplets of incorporated Er3+ were determined based on the Judd–Ofelt treatment of optical absorption spectra recorded at room temperature. Obtained parameters Ωt (t=2, 4, and 6) are 1.47×10−20cm2, 1.38×10−20cm2, and 1.19×10−20cm2 respectively. Low energy crystal levels of Er3+ in GAGG were determined employing absorption and luminescence spectra recorded at 5K. Consequently, the energy diagram constructed was used to substantial discussion of obtained experimental data. Up-conversion of infrared radiation at 980nm into visible emission in crystals co-doped with erbium and ytterbium was observed and discussed. It was concluded that gathered spectroscopic data point at the potential of the GAGG:Yb3+, Er3+ system for application as a laser active material operating around 1500nm within the 4I13/2→4I15/2 transition of Er3+.

Probing the excited state relaxation dynamics of pyrimidine nucleosides in chloroform solution

Ultrafast transient electronic and vibrational absorption spectroscopy (TEAS and TVAS) of 2'-deoxy-cytidine (dC) and 2'-deoxy-thymidine (dT) dissolved in chloroform examines their excited-state dynamics and the recovery of ground electronic state molecules following absorption of ultraviolet light. The chloroform serves as a weakly interacting solvent, allowing comparisons to be drawn with prior experimental studies of the photodynamics of these nucleosides in the gas phase and in polar solvents such as water. The pyrimidine base nucleosides have some propensity to dimerize in aprotic solvents, but the monomer photochemistry can be resolved clearly and is the focus of this study. UV absorption at a wavelength of 260 nm excites a 1ππ* ← S0 transition, but prompt crossing of a significant fraction (50% in dC, 17% in dT) of the 1ππ* population into a nearby 1nπ* state is too fast for the experiments to resolve. The remaining flux on the 1ππ* state leaves the vertical Franck-Condon region and encounters a conical intersection with the ground electronic state of ethylenic twist character. In dC, the 1ππ* state decays to the ground state with a time constant of 1.1 ± 0.1 ps. The lifetime of the 1nπ* state is much longer in the canonical forms of both molecules: recovery of the ground state population from these states occurs with time constants of 18.6 ± 1.1 ps in amino-oxo dC and ∼114 ps in dT, indicating potential energy barriers to the 1nπ*/S0 conical intersections. The small fraction of the imino-oxo tautomer of dC present in solution has a longer-lived 1nπ* state with a lifetime for ground state recovery of 193 ± 55 ps. No evidence is found for photo-induced tautomerization of amino-oxo dC to the imino-oxo form, or for population of low lying triplet states of this nucleoside. In contrast, ∼8% of the UV-excited dT molecules access the long-lived T1 (3ππ*) state through the 1nπ* state. The primary influence of the solvent appears to be the degree to which it destabilizes the states of 1nπ* character, with consequences for the lifetimes of these states as well as the triplet state yields.

Anomalous Size-Dependent Excited-State Relaxation Dynamics of NanoGUMBOS

The synthesis, characterization, and ultrafast spectroscopy of size-selected nanospheres of ruthenium bipyridine–bis(pentafluoroethylsulfonyl)imide ([Ru(bipy)3][BETI]2) in water are reported. These studies represent the first experimental evidence of phonons with nanosecond lifetimes in organometallic nanomaterials. Thermally stable, crystalline nanoparticles of [Ru(bipy)3][BETI]2 are derived from a group of uniform materials based on organic salts (GUMBOS). Excited-state relaxation dynamics are studied using pump–probe time-resolved transient absorption spectroscopy, and the results are compared to corresponding measurements of aqueous Ru(bipy)3Cl2. The nanoGUMBOS show spectral shifts and size-dependent relaxation dynamics for nanoparticle diameters varying from 20 to 100 nm, characterized by excited-state decay dynamics similar to those of the precursor dye at higher pump pulse energies with an additional pathway attributed to intermolecular energy transfer, where all lifetimes increase with increasing ...

Excited‐State Deactivation of Branched Phthalocyanine Compounds

The excited-state relaxation dynamics and chromophore interactions in two phthalocyanine compounds (bis- and trisphthalocyanines) are studied by using steady-state and femtosecond transient absorption spectral measurements, where the excited-state energy-transfer mechanism is explored. By exciting phthalocyanine compounds to their second electronically excited states and probing the subsequent relaxation dynamics, a multitude of deactivation pathways are identified. The transient absorption spectra show the relaxation pathway from the exciton state to excimer state and then back to the ground state in bisphthalocyanine (bis-Pc). In trisphthalocyanine (tris-Pc), the monomeric and dimeric subunits are excited and the excitation energy transfers from the monomeric vibrationally hot S1 state to the exciton state of a pre-associated dimer, with subsequent relaxation to the ground state through the excimer state. The theoretical calculations and steady-state spectra also show a face-to-face conformation in bis-Pc, whereas in tris-Pc, two of the three phthalocyanine branches form a pre-associated face-to-face dimeric conformation with the third one acting as a monomeric unit; this is consistent with the results of the transient absorption experiments from the perspective of molecular structure. The detailed structure-property relationships in phthalocyanine compounds is useful for exploring the function of molecular aggregates in energy migration of natural photosynthesis systems.

Excited state relaxation dynamics and up-conversion phenomena in Gd3(Al,Ga)5O12 single crystals co-doped with holmium and ytterbium

Single crystals of Gd3(Al,Ga)5O12 single doped with Ho3+ or Yb3+ ions and co-doped with Ho3+ and Yb3+ ions were grown by the Czochralski technique and investigated employing methods of optical spectroscopy. Rates of radiative transitions, branching ratio values and radiative lifetimes for excited multiplets of incorporated Ho3+ ions were determined based on the Judd–Ofelt treatment of optical absorption spectra recorded at room temperature. Absorption spectra and luminescence spectra recorded at 5 K made it possible to determine crystal field splitting for several low energy multiplets of Ho3+ ions and for the 2F5/2 multiplet of Yb3+ ions. Lifetimes of luminescent levels of incorporated holmium and ytterbium ions and the Yb3+ − Ho3+ energy transfer efficiency were determined based on analysis of recorded luminescence decay curves. Up-conversion of infrared radiation at 980 nm into yellow emission in crystals co-doped with holmium and ytterbium was observed and discussed. It was found that the structural disorder of the Gd3(Al,Ga)5O12 host resulting from a disparity of ionic radii of Al and Ga ions induces an inhomogeneous broadening of spectral lines of incorporated luminescent ions but the crystal field splitting of their multiplets is similar to that encountered in ordered garnet hosts. Based on analysis of gathered spectroscopic data it was concluded that the Gd3(Al,Ga)5O12:Ho3+,Yb3+ crystals are promising materials for the design of laser-diode pumped infrared lasers operating near 2000 nm.

Excited-state vibrational relaxation and deactivation dynamics of trans-4-(N,N-dimethylamino)-4′-nitrostilbene in nonpolar solvents studied by ultrafast time-resolved broadband fluorescence spectroscopy

Abstract The excited-state relaxation dynamics of trans -4-( N , N -dimethylamino)-4′-nitrostilbene excited to the first absorption band in nonpolar solvents (cyclohexane and n -hexadecane) has been studied with ultrafast time-resolved broadband fluorescence spectroscopy. The temporal evolution of the time-resolved fluorescence spectra and bandwidth narrowing reveal a multiple-stage vibrational relaxation within ∼15 ps followed by slower excited-state deactivation steps (80 and 950 ps in cyclohexane). In addition, an oscillatory fluorescence with a period of about 1.1 ps was observed and attributed to the coherent vibrational motion of the nitrophenyl/aminophenyl torsion that modulates the early-time fluorescence spectra. The decay of the total fluorescence intensity with cubic frequency correction was found to be consistent with a competitive triplet–single deactivation mechanism.

Surface-hopping dynamics simulations of malachite green: a triphenylmethane dye.

Malachite green is a typical triphenylmethane dye widely used in fundamental and industrial research; however, its excited-state relaxation dynamics remains elusive. In this work we simulate its photodynamics from the S2 and S1 states using the fewest-switches surface-hopping scheme. In the S2 photodynamics, the system first relaxes to the S2 minimum, which immediately hops to the S1 state via an S2/S1 conical intersection. In the S1 state, 90% trajectories evolve into a structurally symmetric S1 minimum; the remaining ones proceed toward two propeller-like S1 minima. Two kinds of S1 minima then decay to the S0 state via the S1/S0 conical intersections. The S1 photodynamics is overall similar to the S1 excited-state dynamics as a result of the ultrafast S2 → S1 internal conversion in the S2 photodynamics, but the weights of the trajectories that decay to the S0 state via three different S1/S0 conical intersections are variational. Moreover, the S2 relaxation dynamics mainly happens in a concerted synchronous rotation of three phenyl rings. In comparison, in the S1 relaxation dynamics, the rotations of two aminophenyl rings can proceed in the same and opposite directions. In certain trajectories, only the rotation of an aminophenyl ring is active. On the basis of the results, the S2 and S1 excited-state lifetimes of malachite green in vacuo are calculated to be 424 fs and 1.2 ps, respectively. The present work provides important mechanistic insights for similar triphenylmethane dyes.

Excited-State Dynamics of a D-π-A Type Sulfonium-Based Alkoxystilbene Photoacid Generator

The excited-state relaxation dynamics of a D-π-A sulfonium-based alkoxystilbene photoacid generator has been investigated in acetonitrile solution by using femtosecond transient absorption and nanosecond laser flash photolysis experiments. For the first time, the successive reaction steps involved in the photoinduced proton generation of a sulfonium acid generator have been kinetically and spectrally resolved from the early stages (femtosecond time scale) to the final chemical processes (microsecond domain). An overall four-step reaction scheme is established, and two main deactivation pathways limiting the proton generation efficiency are identified and quantified.

Excited-state relaxation of hydrated thymine and thymidine measured by liquid-jet photoelectron spectroscopy: experiment and simulation.

Time-resolved photoelectron spectroscopy is performed on thymine and thymidine in aqueous solution to study the excited-state relaxation dynamics of these molecules. We find two contributions with sub-ps lifetimes in line with recent excited-state QM/MM molecular dynamics simulations (J. Chem. Phys. 2013, 139, 214304). The temporal evolution of ionization energies for the excited ππ* state along the QM/MM molecular dynamics trajectories were calculated and are compatible with experimental results, where the two contributions correspond to the relaxation paths in the ππ* state involving different conical intersections with the ground state. Theoretical calculations also show that ionization from the nπ* state is possible at the given photon energies, but we have not found any experimental indication for signal from the nπ* state. In contrast to currently accepted relaxation mechanisms, we suggest that the nπ* state is not involved in the relaxation process of thymine in aqueous solution.

Probing deactivation pathways of DNA nucleobases by two-dimensional electronic spectroscopy: first principles simulations.

The SOS//QM/MM [Rivalta et al., Int. J. Quant. Chem., 2014, 114, 85] method consists of an arsenal of computational tools allowing accurate simulation of one-dimensional (1D) and bi-dimensional (2D) electronic spectra of monomeric and dimeric systems with unprecedented details and accuracy. Prominent features like doubly excited local and excimer states, accessible in multi-photon processes, as well as charge-transfer states arise naturally through the fully quantum-mechanical description of the aggregates. In this contribution the SOS//QM/MM approach is extended to simulate time-resolved 2D spectra that can be used to characterize ultrafast excited state relaxation dynamics with atomistic details. We demonstrate how critical structures on the excited state potential energy surface, obtained through state-of-the-art quantum chemical computations, can be used as snapshots of the excited state relaxation dynamics to generate spectral fingerprints for different de-excitation channels. The approach is based on high-level multi-configurational wavefunction methods combined with non-linear response theory and incorporates the effects of the solvent/environment through hybrid quantum mechanics/molecular mechanics (QM/MM) techniques. Specifically, the protocol makes use of the second-order Perturbation Theory (CASPT2) on top of Complete Active Space Self Consistent Field (CASSCF) strategy to compute the high-lying excited states that can be accessed in different 2D experimental setups. As an example, the photophysics of the stacked adenine-adenine dimer in a double-stranded DNA is modeled through 2D near-ultraviolet (NUV) spectroscopy.

Excited-state dynamics of guanosine in aqueous solution revealed by time-resolved photoelectron spectroscopy: experiment and theory.

Time-resolved photoelectron spectroscopy is performed on aqueous guanosine solution to study its excited-state relaxation dynamics. Experimental results are complemented by surface hopping dynamic simulations and evaluation of the excited-state ionization energy by Koopmans' theorem. Two alternative models for the relaxation dynamics are discussed. The experimentally observed excited-state lifetime is about 2.5 ps if the molecule is excited at 266 nm and about 1.1 ps if the molecule is excited at 238 nm. The experimental probe photon energy dependence of the photoelectron kinetic energy distribution suggests that the probe step is not vertical and involves a doubly-excited autoionizing state.

A wavelength dependent investigation of the indole photophysics via ionization and fragmentation pump-probe spectroscopies.

A wavelength dependent study investigating the low-lying (1)La and (1)Lb states, both possessing (1)ππ* character, and the (1)πσ* state in the deactivation process of indole is presented here. Relaxation dynamics following excitation at 241, 250, 260, 270, 273, and 282 nm are examined using three gas-phase, pump-probe spectroscopic techniques: (1) hydrogen atom (H-atom) time-resolved kinetic energy release (TR-KER), (2) time-resolved photoelectron spectroscopy (TR-PES), and (3) time-resolved ion yield (TR-IY). Applied in combination, a more complete picture of the indole relaxation dynamics may be gleaned. For instance, TR-PES experiments directly observe all relaxation pathways by probing the evolution of the excited states following photoexcitation; whereas, TR-KER measurements indirectly, yet specifically, probe for (1)πσ*-state activity through the detection of H-atoms eliminated along the indole nitrogen-hydrogen (N-H) stretch coordinate-a possible outcome of (1)πσ*-state relaxation in indole. In addition, mass information obtained via TR-IY monitors fragmentation dynamics that may occur within the neutral electronically excited and/or cationic states. The work herein assesses the onset and importance of the (1)πσ* state at various pump wavelengths by systematically tuning across the ultraviolet absorption spectrum of indole with a particular focus on those pump wavelengths longer than 263 nm, where the involvement of the (1)πσ* state is under current debate. As far as this experimental work is concerned, there does not appear to be any significant involvement by the (1)πσ* state in the indole relaxation processes following excitation at 270, 273, or 282 nm. This investigation also evaluates the primary orbital promotions contributing to the (1)La, (1)Lb, and (1)πσ* transitions based on ionization preferences observed in TR-PES spectra. Relaxation time constants associated with dynamics along these states are also reported for excitation at all of the aforementioned pump wavelengths and are used to pinpoint the origin of the discrepancies found in the literature. In this context, advantages and disadvantages of the three experimental techniques are discussed.

Distinct roles of the photosystem II protein PsbS and zeaxanthin in the regulation of light harvesting in plants revealed by fluorescence lifetime snapshots.

The photosystem II (PSII) protein PsbS and the enzyme violaxanthin deepoxidase (VDE) are known to influence the dynamics of energy-dependent quenching (qE), the component of nonphotochemical quenching (NPQ) that allows plants to respond to fast fluctuations in light intensity. Although the absence of PsbS and VDE has been shown to change the amount of quenching, there have not been any measurements that can detect whether the presence of these proteins alters the type of quenching that occurs. The chlorophyll fluorescence lifetime probes the excited-state chlorophyll relaxation dynamics and can be used to determine the amount of quenching as well as whether two different genotypes with the same amount of NPQ have similar dynamics of excited-state chlorophyll relaxation. We measured the fluorescence lifetimes on whole leaves of Arabidopsis thaliana throughout the induction and relaxation of NPQ for wild type and the qE mutants, npq4, which lacks PsbS; npq1, which lacks VDE and cannot convert violaxanthin to zeaxanthin; and npq1 npq4, which lacks both VDE and PsbS. These measurements show that although PsbS changes the amount of quenching and the rate at which quenching turns on, it does not affect the relaxation dynamics of excited chlorophyll during quenching. In addition, the data suggest that PsbS responds not only to ΔpH but also to the Δψ across the thylakoid membrane. In contrast, the presence of VDE, which is necessary for the accumulation of zeaxanthin, affects the excited-state chlorophyll relaxation dynamics.

Effect of temperature on excited state relaxation dynamics and up-conversion phenomena in La3Ga5.5Ta0.5O14:Er3+ single crystals

The La3Ga5.5Ta0.5O14 (LGT) single crystals nominally doped with 5at.% and 1at.% of Er3+ were grown by the Czochralski method in an atmosphere of nitrogen containing small amount of oxygen. Examination of the grown crystals employing a coupled plasma emission spectroscopy (ICP ES) revealed that actual concentrations of Er3+ ions amount to 3.8at.% and 0.27at.%, respectively. Absorption and emission spectra as well as relaxation of excited states of Er3+ ions in the LGT host were investigated as a function of temperature in the 300–700K temperature region. The main attention was focused on spectroscopic properties of the LGT:Er crystal that are relevant to a potential laser operation associated with the 4I13/2→4I15/2 transition of Er3+ near 1.6μm and to up-conversion of infrared radiation into green luminescence originated in the 2H11/2, 4S3/2 levels. It was found that the increase of temperature affects weakly spectral features of inhomogeneously broadened absorption bands related to the 4I15/2→4I11/2 and 4I15/2→4I13/2 transitions. Observed decrease of the 4I11/2 lifetime is consistent with calculated dependence assuming the contribution of multiphonon relaxation process that involves emission of 5 phonons with energy of 660cm−1. Decrease of lifetime for the 2H11/2, 4S3/2 group of levels with increasing temperature, calculated assuming thermalization effects and the contribution of multiphonon relaxation, is slightly slower than experimental dependence, however. Integrated intensity of up-converted green emission excited at 980nm diminishes quickly with increasing temperature and becomes hardly visible already at 670K. It is supposed that this is due to simultaneous decrease of quantum efficiencies of both the intermediate 4I11/2 level and luminescent 2H11/2, 4S3/2 group of levels.

Optical properties of crystals doped with Sm3+ or Dy3+ relevant to potential InGaN/GaN laser diode-pumped visible laser operation: A comparative study

Results of detailed spectroscopic investigation of Sm3+ and Dy3+ ions incorporated in crystal structures of Yal YAl3(BO3)4, LiNbO3, Gd3Ga5O12, Gd2SiO5, Lu2SiO5 and (Gd, Lu)2SiO5 are reported and discussed. The impact of the hosts on transition intensities and excited state relaxation dynamics of incorporated luminescent ions was examined. Distribution of luminescence intensity among spectral bands in terms of luminescence branching ratios was evaluated based on numerical integration of luminescence bands. Intensities of UV and blue absorption bands potentially useful for optical pumping were determined quantitatively in units of absorption cross section. The most intense luminescence bands related to potential laser transitions 4 G 5/2 → 6 H 7/2 of Sm3+ around 600 nm and 4 F 9/2 → 6 H 13/2 of Dy3+ around 580 nm were calibrated in units of emission cross section. Evaluated peak values of emission cross section range from 0.43 × 10−20 cm2 for Sm3+ in (Gd, Lu)2SiO5 to 1.17 × 10−20 cm2 for Sm3+ in LiNbO3. Those for dysprosium-doped crystals range from 0.63 × 10−20 cm2 for LiNbO3:Dy3+ to 2.0 × 10−20 cm2 for Yal YAl3(BO3)4:Dy3+. It follows from these considerations that samarium-doped crystals show promise for laser application owing to the combination of a strong absorption that matches radiation of commercial laser diodes emitting near 405 nm and long luminescence lifetime. Major shortcoming of dysprosium-doped crystals results from a weak intensity of absorption bands available for optical pumping near 450 nm and 385 nm combined with relatively strong self-quenching of luminescence.