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A theoretical treatment based on the equations of motion of an electronic reduced density matrix, and related computational modeling, is used to describe and calculate relaxation times for nanostructured TiO2(110) surfaces, here for Ag and Ag2 adsorbates. The theoretical treatment deals with the preparation of a photoexcited system under two different conditions, by steady light absorption with a cutoff and by a light pulse, and describes the following relaxation of electronic densities. On the computational modeling, results are presented for electronic density of states, light absorbance, and relaxation dynamics, comparing results for Ag and Ag2 adsorbates. The aim of this work is to provide insight on the dynamics and magnitude of relaxation rates for a surface with adsorbed open- and closed-shell Ag species to determine whether the advantages in using them to enhance light absorbance remain valid in the presence of charge density relaxation. Different behaviors can be expected depending on whether the adsorbate particles (Ag metal clusters in our present choice) have electronic open-shell or closed-shell structures. Calculated electron and hole lifetimes are given for pure TiO2(110), Ag/TiO2(110), and Ag2/TiO2(110). The present results, while limited to chosen structures and photon wavelengths, show that relaxation rates are noticeably different for electrons and holes, but comparable in magnitude for pure and adsorbate surfaces. Overall, the introduction of the adsorbates does not lead to rapid loss of charge carriers, while they give large increases in light absorption. This appears to be advantageous for applications to photocatalysis. [ABSTRACT FROM AUTHOR]

A theoretical treatment based on the equations of motion of an electronic reduced density matrix, and related computational modeling, is used to describe and calculate relaxation times for nanostructured TiO2(110) surfaces, here for Ag and Ag2 adsorbates. The theoretical treatment deals with the preparation of a photoexcited system under two different conditions, by steady light absorption with a cutoff and by a light pulse, and describes the following relaxation of electronic densities. On the computational modeling, results are presented for electronic density of states, light absorbance, and relaxation dynamics, comparing results for Ag and Ag2 adsorbates. The aim of this work is to provide insight on the dynamics and magnitude of relaxation rates for a surface with adsorbed open- and closed-shell Ag species to determine whether the advantages in using them to enhance light absorbance remain valid in the presence of charge density relaxation. Different behaviors can be expected depending on whether the adsorbate particles (Ag metal clusters in our present choice) have electronic open-shell or closed-shell structures. Calculated electron and hole lifetimes are given for pure TiO2(110), Ag/TiO2(110), and Ag2/TiO2(110). The present results, while limited to chosen structures and photon wavelengths, show that relaxation rates are noticeably different for electrons and holes, but comparable in magnitude for pure and adsorbate surfaces. Overall, the introduction of the adsorbates does not lead to rapid loss of charge carriers, while they give large increases in light absorption. This appears to be advantageous for applications to photocatalysis. [ABSTRACT FROM AUTHOR]

Mechanical spectral hole burning (MSHB) has been used to investigate the nonlinear dynamics in polymers, ranging from melts, solutions, block co-polymers, and glasses. MSHB was developed as an analog to the dielectric spectral hole burning method, which is not readily applicable in polymers due to weak dielectric response. While similar holes were observed in both mechanical and dielectric hole burning, the interpretations were different. In the latter case, it has been argued that the holes are related to dynamic heterogeneity as related to an increase in the local temperature of molecular sub-ensembles (spatial heterogeneity), while in the former case, the holes have been related to the type of dynamics (rubbery, Rouse, etc.). Recent work from our laboratories used MSHB to investigate glassy poly(methyl methacrylate) and showed evidence of hole burning and supported the hypothesis that the origin of holes was related to dynamic heterogeneity as evidenced by the holes being developed near the strong β-relaxation in PMMA. In this work, MSHB is used to study polycarbonate, which has a weak β-relaxation, and the results are compared with those observed in PMMA. We observe that the polycarbonate exhibits weak holes and the nature of the holes with a change in pump amplitude and frequency is different than observed in PMMA. These results support the hypothesis that the hole burning observed in amorphous polymers below the glass transition temperature is related to the strength of the β-transition, which, in turn, is related to molecular level heterogeneity in the material dynamics. [ABSTRACT FROM AUTHOR]

Nonlinear mechanics of soft materials such as polymer melts or polymer solutions are frequently investigated by Large Amplitude Oscillatory Shear (LAOS) spectroscopy tests. Less work has been reported on the characterization of the nonlinear viscoelastic properties of glassy polymers within a similar framework. In the present work, we use an extension of LAOS, i.e., mechanical spectral hole burning (MSHB), to investigate the nonlinear dynamics of an amorphous polymer in the deep glassy state. MSHB was developed as an analog to non-resonant spectral hole burning developed by Schiener et al. [Science 274(5288), 752–754 (1996)], who attributed the presence of holes to dynamic heterogeneity. On the other hand, Qin et al. [J. Polym. Sci., Part B: Polym. Phys. 47(20), 2047–2062 (2009)] in work on polymer solutions of tailored heterogeneity have attributed the presence of holes to the type of dynamics (Rouse, rubbery, etc.) rather than to a specific spatial heterogeneity. Here, we have performed MSHB experiments on poly(methyl methacrylate) in the deep glassy state (at ambient temperature, which is near to the β-relaxation) to investigate the presence and origin of holes, if any. The effects of pump frequency and pump amplitude were investigated, and we find that vertical holes could be burned successfully for frequencies from 0.0098 Hz to 0.0728 Hz and for pump amplitudes from 2% to 9% strain. On the other hand, horizontal holes were incomplete at high pump amplitude and low frequency, where higher spectral modification is observed. The results are interpreted as being related to the dynamic heterogeneity corresponding to the β-relaxation rather than to the hysteresis energy absorbed in the large deformation pump. [ABSTRACT FROM AUTHOR]

Holes burnt into the absorption spectrum of terrylene in hexadecane have quite unusual features: spectral diffusion behavior under thermal cycles shows a narrowing regime at very low temperatures (2–5 K) followed by a plateau region (up to about 13 K) and a broadening regime (T>13 K). Thermal line broadening (quasihomogeneous linewidth) shows a nonmonotonous behavior as a function of temperature: at around 4 K there is a maximum followed by a flat minimum and the onset of strong broadening at higher temperatures. Finally, the central hole shows one-sided narrowly spaced side features. This behavior is interpreted within the frame of a two-site model. One of the two sites can be well described by a standard two level system; the other, however, shows characteristic features of a multilevel system. The two sites are characterized by strongly different optical linewidths, phototransformation yields, and thermal stabilities. [ABSTRACT FROM AUTHOR]

The hole burning spectra of phenol/ammonia (1:3 and 1:4) clusters were measured by a newly developed four-color (UV–near-IR–UV–UV) hole burning spectroscopy, which is a kind of population labeling spectroscopy. From the hole burning spectra, it was found that single species is observed in an n=3 cluster, while three isomers are observed simultaneously for n=4. A possibility was suggested that the reaction efficiency of the hydrogen transfer from the electronically excited phenol/ammonia clusters, which was measured by a comparison with the action spectra of the corresponding cluster, depends on the initial vibronic levels. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The response to the field sequence of nonresonant hole burning, a pump-wait-probe experiment originally designed to investigate slow relaxation in complex systems, is calculated for a model of Brownian oscillators, thus including inertial effects. In the overdamped regime the model predictions are very similar to those of the purely dissipative stochastic models investigated earlier, including the possibility to discriminate between dynamic homogeneous and heterogeneous relaxation. The case of underdamped oscillations is of particular interest when low-frequency excitations in glassy systems are considered. We show that also in this situation a frequency selective modification of the response should be feasable. This means that it is possible to specifically address various parts of the spectrum. An experimental realization of nonresonant holeburning in the Terahertz regime therefore is expected to shed further light on the nature of the vibrations around the so-called boson peak. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Transient, nonresonant, hole-burning spectroscopy has been used to study the charge recombination process in poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1-4-phenylene vinylene] (MDMO-PPV): methanofullerene (PCBM) composite films. The position and intensity of the spectral hole in the absorption band of MDMO-PPV have been monitored as a function of time in the 10 ns–10 μs time range. A time-dependent redshift is observed. The intensity of the spectral hole decays with time according to a power law (∝t[sup -α]). The exponent α≈0.5 is found to be nearly independent of the excitation fluence in the range 0.05–2 mJ/cm2. The depth of the spectral hole depends sublinearly on the excitation fluence (I) and can be described by (∝Γ[sup -β]) with β∼0.5. The time-dependent redshift and the power-law type time decay can be reproduced by numerical simulations. The Monte Carlo method is used to simulate the hopping dynamics of the photoinduced charges in a lattice of energetically disordered sites before they eventually recombine at the MDMO-PPV:PCBM interface. The results indicate that charge separation is assisted by disorder and that, in the 10 ns–10 μs time range, the recombination rate is limited by the detrapping of the cationic charge carriers in MDMO-PPV. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have calculated the effects of dielectric hole burning on the basis of the frequency dependent dielectric relaxation [variant_greek_epsilon]⁁(ω) and specific heat c⁁[sub p](ω) of glycerol and assuming heterogeneous dynamics where the dielectric and thermal relaxation times are correlated quantities. The heat generated in the sample is determined from the time dependent electric field and polarization, i.e., without involving steady-state approximations. The calculations mimic the protocol of recent hole-burning experiments on glycerol [K. Duvvuri and R. Richert, J. Chem. Phys. 118, 1356 (2003)], including the high-field burn-process, the phase-cycle employed to eliminate the linear response to the high field, the detection in terms of the electric modulus M(t), and the signal normalization. Without using any fit parameters, this model is capable of quantitatively reproducing the amplitudes, shapes, and peak positions of observed dielectric holes, together with their dependence on the burn frequency and the waiting time between the pump and probe processes. Therefore, frequency selective local heating of the modes of motion associated with the structural relaxation resulting from the dielectric loss fully accounts for the dielectric hole burning effects. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We performed spectral hole burning experiments in the UV with p-chlorotoluene as a probe in cyclohexane. A method is presented which allows for the determination of the rotational tunneling splitting in SO and S[sub 1]. The respective values are (117±4) GHz (3.90±0.13) cm[sup -1] and (84 ± 4) GHz (2.80±0.13)cm[sup -1]. From these numbers the rotational barriers and the respective rotational eigenvalues can be determined. Based on these results the spin conversion dynamics is reinterpreted as being governed by Orbach processes. [ABSTRACT FROM AUTHOR]

Focuses on the results of the induction of persistent spectral hole burning in the zinc excitonic absorption band of cupric bromide semiconductor nanocrystals in glass. Details of the selective excitation with nanosecond dye-laser pulses at low temperatures; Observation of effects in samples containing nanocrystals with mean radius smaller than nanometer.

Explores the use of the method of dielectric hole burning to distinguish a homogenous broadened spectrum from a distribution of relaxation times in a dielectric material. Time-dependent shift of the response function; Effect of a frequency selective absorption of energy on local fictive temperature.

Analyzes the vibronic spectra of jet cooled phenol(H[sub 2])[sub 7.8] clusters with mass selective resonance enhanced two photon ionization and ultraviolet-ultraviolet spectral hole burning. Use of a double resonance technique with an infrared laser as burn laser to measure the intramolecular OH stretching vibrations of the mass- and isomer-selected clusters.

Studies transient spectral hole burning and hydrogen-bond breaking determined in different solutions of ethanol in deuterated ethanol. Lifetime of the OH mode of associated ethanol; Thermal effect due to the deposited energy.

With infrared transient hole-burning spectroscopy we have investigated the influence of OD···X hydrogen bonds on the vibrational line shape of O–D stretch vibrations in acid zeolites. The effect of hydrogen bonding on the line shape depends critically on the type of hydrogen bond. For hydrogen bonding in a rigid structure, the hydrogen bond determines the inhomogeneous linewidth, but the homogeneous linewidth is determined by coupling to a ∼200 cm-1 lattice mode as concluded from the temperature dependence of the dephasing rate. When the hydrogen bond is formed with an adsorbing molecule, the coupling between the high-frequency O–D stretch vibration and the low-frequency OD···X hydrogen-bond stretching mode does determine the homogeneous linewidth. The difference between the two systems can be explained by the different hydrogen-bond potentials. Variation of the adsorbate provides a means of obtaining conclusive information on the coupling mechanism between the high-frequency O–D stretching mode and the low-frequency OD···X hydrogen-bond stretching mode. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Inter- and intramolecular vibrations of the Phenol dimer have been examined using spectral hole burning and dispersed fluorescence spectroscopy. The dispersed fluorescence spectra have been recorded via excitation of the electronic donor origin and all intermolecular vibrational transitions. The Franck–Condon intensity pattern allowed a straightforward assignment of the ground state vibrational frequencies to the excited state frequencies, which were examined by hole-burning spectroscopy. The existence of another conformer that possibly absorbs in the region of interest was ruled out by hole-burning spectroscopy. For obtaining the hole-burning spectra, the electronic origin of the donor chromophore was analyzed, while the hole-burning laser was scanned over the region of interest. As both acceptor and donor part belong to one molecule the hole-burning signal could be analyzed via fluorescence from one of the chromophores. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The ground and first excited states of the organic dyes quinizarin (Q) and tetrahydroxyphenylporphyrin (TOHP) chemisorbed on γ-Al2O3 were investigated with semiempirical PM3 and multireference CI methods. Q/γ-Al2O3 and TOHP/γ-Al2O3 represent promising materials for frequency domain optical data storage (FDOS) based on persistent spectral hole burning (PSHB), since it is possible to detect spectral holes at high temperatures (77 K). To find out whether differences in the electronic structure between the free and the adsorbed molecules account for the hole-burning properties, we performed calculations of Q–Al complexes with various coordination spheres. The calculated vertical excitation energies for the first electronically excited state of the investigated structures are in good agreement with experimental data. Analysis of the molecular orbitals shows that complexation of the investigated molecules with Al affects the electronic structure of the dyes only little. Furthermore, the character of the first excited state is conserved. The change of the dipole moment between the ground and the first excited states is about the same for the free and for the complexated systems. Therefore, it is concluded that hole burning of dye molecules chemisorbed on γ-Al2O3 at high temperatures is not due to a change of the electronic structure of the adsorbed dye molecules compared to the free dye molecules, but has to be attributed to the special interactions of Q with the γ-Al2O3 surface. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The phenol-ammonia 1:1 complex has been investigated by mass resolved hole burning spectroscopy and ab initio methods at the HF/6-31G(d,p) and HF/6-31++G(d,p) levels of theory. By means of spectral hole burning four bands in the region of intermolecular vibrations could be assigned to the 1:1 complex. The ab initio computed cluster structure and its normal vibrations are reported and compared to the experimental results. Anharmonic calculations were carried out for the ammonia torsion. The results are compared to structurally related complexes. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We measured the pressure-induced shift and broadening of spectral holes for 14 different impurity sites in a polycrystalline solid solution of chlorin (17,18-dihydro-21H,23H-porphine) in benzophenone. In addition, we investigated the glassy phase of the same system in a frequency range which covered the entire inhomogeneously broadened band. The temperature range of the experiments was between 1.5 and 4.2 K. Pressure levels up to 10 MPa were applied. In the glassy phase, we observed a linear frequency dependence of the shift per pressure. However, in the crystalline phase, the general trend of the data clearly indicated a nonlinear frequency dependence. Yet, the individual sites, especially those with lower frequencies, showed a kind of stochastic scattering around the general trend behavior. The results were interpreted within the frame of existing models. The experiments demonstrate that matrix isolation combined with hole burning spectroscopy of large molecular impurities in polymorphic host materials under varying pressure conditions is a useful technique for determining molecular as well as bulk parameters, for examining problems of microelasticity and microplasticity, and for investigating the fundamental differences between glasses and crystals. [ABSTRACT FROM AUTHOR]

Zero field absorption detected magnetic resonance hole burning measurements were performed on photosynthetic reaction centers of the bacteria Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis. Extrapolation to zero microwave power yielded pseudohomogeneous linewidths of 2.0 MHz for Rhodopseudomonas viridis, 1.0 and 0.9 MHz for the protonated forms of Rhodobacter sphaeroides R26 with and without monomer bacteriochlorophyll exchanged, and 0.25 MHz as an upper limit for fully deuterated reaction centers of Rhodobacter sphaeroides R26. The measured linewidths were interpreted as being due to unresolved hyperfine interaction between the nuclear spins and the triplet electron spin, the line shape being determined by spectral diffusion among the nuclei. The difference in linewidths between Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis is then explained by triplet delocalization on the special pair in the former, and localization on one dimer half on the latter. In the fully deuterated sample, four quadrupole satellites were observed in the hole spectra arising from the eight 14N nitrogens in the special pair. The quadrupole parameters seem to be very similar for all nitrogens and were determined to κ=1.25±0.1 MHz and η=0.9±0.1 MHz. [ABSTRACT FROM AUTHOR]

Spectral hole burning is used to measure spin-conversion relaxation of methyl groups attached to a dye probe. The dye is dimethyl-s-tetrazine, the host is n-octane, which is, at low temperatures, a Shpol’skii-matrix. The temperature dependence of the spin-conversion relaxation follows the same pattern for the protonated and the perdeuterated methyl-rotor. However, the relaxation rates of the perdeuterated rotor are higher by almost two orders of magnitude. Partial deuteration destroys the rotor symmetry and leads to a breakdown of the correlation between nuclear spin and rotational wave function. [ABSTRACT FROM AUTHOR]

The behavior of spectral holes under pressure in a polycrystalline material, namely dimethyl-s-tetrazine (DMST) doped n-octane was investigated and compared with the behavior in a durene single crystal host and glasses. Application of pressure induces frequency shifts and line broadenings which are significantly larger than in single crystals and glasses. Part of the broadening is irreversible and is attributed to the creation of dipolar strain fields. The distribution of dislocation thresholds is continuous with no obvious lower cut off. The response of the material to pressure changes depends on its history. [ABSTRACT FROM AUTHOR]

High-resolution, fast optical hole-burning results are reported for the amorphous system cresyl violet in ethanol glass at 1.3 K. Holes are burned and detected using a novel technique which allows precise detection of narrow (∼0.03 cm-1 ), shallow (∼1%) holes 10 μs to 50 ms after their generation. The technique is described in detail along with careful tests demonstrating the validity of its results. The hole width is observed to increase linearly with time when plotted against log time. Using the four time correlation function description of optical hole burning, the time-dependent increase in hole width (spectral diffusion) is shown to arise from a broad distribution of fluctuation rates in the glass with the probability of having a fluctuation at rate R proportional to 1/R. The 10 μs to 50 ms data is combined with hole-width data spanning the range 100 ms to 10 000 s and with two-pulse picosecond photon echo data. The two-pulse photon echo linewidth is calculated by extrapolating the fluctuation rate distribution obtained from the hole-width data to short times. The results are in excellent agreement with experimental echo results. The combined data from the two sets of hole-burning experiments provides a detailed description of the glass dynamics over nine decades of time, 10 000 s to 10 μs. Together with the two-pulse photon echo results, the data provide information on the glass dynamical behavior over seven decades faster in time as well. The net result is a description of the dynamics in low-temperature ethanol glass on time scales spanning 16 decades. [ABSTRACT FROM AUTHOR]

A number of limitations to hole burning in the liquid phase are identified. As spectral diffusion becomes more rapid, a point is reached where the narrowest hole width no longer measures the homogeneous linewidth. Spectral congestion of the solute is also shown to limit the fastest detectable spectral diffusion rate. An optimal pulse length is found which allows observation of the most rapid spectral diffusion. In addition, the coherence effect observed when the pulses overlap is shown to have resonances at both the excited and ground state vibrational spacings. The coherence effect greatly resembles the hole burning spectrum, but contains no dynamical information. Because of these limitations, hole burning may not be observed even when the homogeneous spectrum is well resolved and spectral diffusion is slow. Experimental confirmation is found in the hole burning spectrum of iodine in hexane, which shows no hole burning despite having a narrow homogeneous linewidth. [ABSTRACT FROM AUTHOR]

We measured thermally irreversible line broadening features of photochemical holes burnt into a phthalocyanine doped Shpol’skiiˇ crystal. The broadening, as obtained from temperature cycling hole burning experiments is significant, indicating that irreversible structural changes do occur in Shpol’skiiˇ matrices. Different sites show a different behavior. As far as line broadening is concerned, the observed features are similar to glasses. The thermal recovery curve of the holes, however, differs very much from glasses. It can be fitted by a bimodal Gaussian distribution. This bimodal distribution is interpreted in terms of two categories of photoproduct states, which the phthalocyanine molecule can possibly occupy: In category one, the two inner protons are neighbors in category two, they are diagonal. [ABSTRACT FROM AUTHOR]

Nonphotochemical hole burning in glassy host/guest matrices generates a change of the site energy distribution of the guest molecules. This distribution of shifted energies has been determined by deconvoluting the difference of white-light excited fluorescence spectra before and after hole burning. For this aim, a special numeric algorithm has been developed. For the host/guest-system tetracene in ethanol, the observed shifts are within the inhomogeneously broadened line, but a shift to higher energies is predominant and amounts to about 20 wave numbers. [ABSTRACT FROM AUTHOR]

The electric field induced superposition of holograms recorded by spectral hole burning is investigated. Holograms have been burned at adjacent positions in a plane defined by wavelength and electric field. Application of an appropriate electric field to the sample causes the components of adjacent holograms to overlap as the spectral holes split due to Stark shifts of molecular transition frequencies. The diffraction efficiency of such superimposed holograms depends on their relative phase and has been studied theoretically and experimentally. It is shown that for zero phase difference, constructive interference leads to a strong diffraction efficiency whereas for a phase difference of π, the gratings cancel leading to zero diffraction efficiency. Experiments have been performed with the dye cresyl violet in a polyvinylbutyral film at a temperature of 1.7 K and the data are compared with computer simulations. [ABSTRACT FROM AUTHOR]

The first paper in this series presented a detailed analysis of the diffraction efficiency of a single holographic grating obtained by spectral hole burning. This paper covers the influence of phase changes which occur during the burning of a single hologram, and the interaction of spectrally adjacent two laser induced gratings. A theoretical description of the holographic efficiencies which takes into account the influence of the relative phases between the two gratings. Experimental results are presented and discussed in terms of the theory. [ABSTRACT FROM AUTHOR]

The nonplanar structure of the electronic ground state of 5,10 dihydrophenazine (PH2) is responsible for a distribution of sites of PH2 observed upon doping into molecular crystals. The change in molecular geometry of PH2 following optical excitation results in considerable stress at the respective crystalline site, which is compensated by guest reorientation. Photochemical hole burning experiments suggest that this reorientation involves the 118 cm-1 butterfly backbone vibration of PH2 as indicated by a hole width equivalent to a vibrational relaxation time of 600 fs. [ABSTRACT FROM AUTHOR]

Thermal broadening of spectral holes burnt into excitonic states of long chain molecular aggregates of pseudoisocyanine iodide is investigated over a temperature range from 350 mK to 80 K. The results differ very much from the usual behavior of small molecules in glasses. We found that extended states are almost completely decoupled from the amorphous host lattice and spectral diffusion effects play a minor role. The homogeneous linewidth is independent of temperature below 10 K. Above, thermal broadening occurs in two steps: there is a weak onset around 15 K and a strong onset around 65 K. The data can be fitted by a superposition of two exponentials. [ABSTRACT FROM AUTHOR]

Holographic detection is compared with the more common transmission method. The signal shapes of the optical holes determined by both techniques are studied theoretically and experimentally as a function of the burning fluence. From a comparison of the transmission signals and the holographic signals, the homogeneous linewidth can be determined. Experimental data was obtained from free base chlorin (1,2-dihydroporphyrin) in a polyvinylbutyral film at a temperature of 1.7 K. From these measurements a homogeneous linewidth of 350 MHz was determined. Limits of sensitivity of the holographic detection method are discussed. [ABSTRACT FROM AUTHOR]

Theory based on a configuration coordinate model is presented to clarify solute–solvent relaxation effect on the line shape of a time-resolved hole-burning spectrum. The time-resolved hole-burning spectrum is affected by both a hole created in a ground-state population and an excess excited-state population. The solute–solvent relaxation causes thermalization in both populations and then the shift and broadening of the spectrum is expected observable. The line shapes of three typical cases are mainly considered: (1) The excited state is assumed to have an infinitely long lifetime; (2) the excited state has a finite lifetime, the population being assumed to relax toward an electronic state other than the ground state, and (3) the population created in the excited state relaxes to the ground state, where a hole-filling effect is taken into account. Results obtained by numerical calculations show that a time evolution of the ground-state hole is clearly observed when the low-energy tail of the absorption band is excited under the condition that the population decay to the other electronic state is very fast. Further, it is predicted that the hole-filling effect causes a considerable deformation of the spectral shape when the solvent relaxation rate is comparable to the excited-state population decay rate. [ABSTRACT FROM AUTHOR]

Doppler-free spectra of two vibronic bands in the A (1B3u)←X (1Ag) transition of the photochemically instable s-tetrazine (H2C2N4) are presented. For the first time saturation spectroscopy is successfully applied to a large polyatomic molecule. Photochemical decomposition of s-tetrazine molecules takes place after excitation and prevents the molecule from returning to the ground state by radiation and nonradiative processes. This represents a particular type of hole burning in the ground state velocity distribution. The elimination of the inhomogeneous Doppler broadening enables us to determine collisionless homogeneous linewidths. For the 0–0 band a value of γ=190 MHz is found whereas the 16a11 band at higher excess energy (ν’16a =256 cm-1) shows a sharper linewidth of γ=140 MHz. No rotational dependence of the linewidth is found in the 0–0 band up to J levels higher than 70. It is argued that internal conversion to the X (1Ag) state is the process responsible for the observed linewidths and that dissociation takes place on the electronic ground state potential surface. [ABSTRACT FROM AUTHOR]

Investigates the N-D stretching bands of NH[sub 3]D[sup +] ions doped into ammonium tartrate. Use of spectral hole burning in the study; Similarity of energy imparted to ammonium ion and energy required to surmount the reorientation barrier; Discovery of tunneling reactions in the analysis.

Studies the nonresonant dielectric hole burning spectroscopy of supercooled liquids. Background on the principle of nonresonant spectral hole burning (NSHB); Focus on concepts needed for the description of NSHB; Excitation profiles and internal energy scales; Shape of spectral holes; Buildup and refilling of spectral modifications.

Discusses the theory of optical photon echo and hole burning spectroscopies in low temperature glasses. Two-level system and sudden jump models; Hu-Walker equations; Two-pulse echo; Three-pulse echo amplitude; Reproduction of temperature dependence of the two-pulse echo decay rate.

The effects of deuteration on hole burning of aluminum phthalocyanine tetrasulfonate (APT) in glassy films of water is reported. Deuteration has no effect on the zero phonon hole width of the APT electronic transition, but a large effect on the hole burning kinetics. These effects are discussed in terms of the two level systems of glassy water. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

By measuring the reduction of a spectral hole burnt at 500 mK due to temperature cycling experiments, we show that the lower bound of the distribution function of barrier heights is below 10 cm-1. [ABSTRACT FROM AUTHOR]

Persistent optical hole-burning spectroscopy has been conducted for a dye molecule within a very small (∼1 nm) reverse micelle at room temperature. The spectra show a spectral narrowing due to site-selective excitation. This definitely demonstrates that the surroundings of the dye molecule are in a glassy state regardless of a solution at room temperature. On the other hand, the hole-burning spectra exhibit large shifts from excitation frequencies, and their positions are almost independent of excitation frequencies. The hole-burning spectra have been theoretically calculated by taking account of a vibronic absorption band of the dye molecule under the assumption that the surroundings of the dye molecule are in a glassy state. The calculated results agree with the experimental ones that were obtained for the dye molecule in a polymer glass for comparison, where it has been found that the ratio of hole-burning efficiencies of vibronic- to electronic-band excitations is quite high. On the other hand, the theoretical results do not explain the large spectral shift from the excitation frequency and small spectral narrowing observed in the hole-burning spectra measured for the dye-containing reverse micelle. It is thought that the spectral shift and broadening occur within the measurement time owing to the relaxation process of the surroundings that are hot with the thermal energy deposited by the dye molecule optically excited. Furthermore, the relaxation should be temporary because the cooling of the inside of the reverse micelle takes place with the dissipation of the excess thermal energy to the outer oil solvent, and so the surroundings of the dye molecule return to the glassy state and do not attain the thermal equilibrium. These results suggest that a very small reverse micelle provides a unique reaction field in which the diffusional motion can be controlled by light in a glassy state. [ABSTRACT FROM AUTHOR]

The first observation of hole burning in the optical spectra of delocalized polymer backbone states is reported. The polymer chosen for this study is poly-(di-n-hexyl)-silane, consisting of chains of roughly 5100 silicon atoms. Absorption spectra of polysilane in solution at 1.6K and 77K are reported.(AIP) [ABSTRACT FROM AUTHOR]

Reports on the observation of photophysical hole burning (PPHB) on solutions of triphenylmethane dyes at room temperature with ns laser pulse. PPHB in the ground state absorption band of crystal violet in the liquid phase at room temperature; Diameter of the excitation light pulse.

Zero-phonon hole (ZPH) profiles and hole spectra that span about eight decades of burn fluence are reported for Al-phthalocyanine tetrasulphonate in hyperquenched glassy water (HGW) films at 5.0 K. The profiles of unsaturated zero-phonon holes (low burn fluence stage) are more sharply tipped than a Lorentzian. It is shown that the non-Lorentzian behavior is a natural consequence of the interplay between the three distributions that govern the dispersive kinetics of nonphotochemical hole growth. They are denoted by λ, α, and ω, where λ is the tunnel parameter associated with nonphotochemical hole burning (NPHB) and α is the angle between the transition dipole and the laser polarization. The ω distribution stems from off-resonant absorption of the zero-phonon line (ZPL). The single site absorption spectrum used in the calculations included the ZPL and the phonon sideband. The contribution of a distribution of homogeneous ZPL widths to the non-Lorentzian behavior was assessed and found to be negligible compared to that of the above distributions. The burn fluence dependence of the hole spectra, which include the ZPH, phonon sideband, and antihole structures, leads to new insights on the mechanism of NPHB, ones that necessitate modification of the Shu-Small mechanism [L. Shu and G. J. Small, J. Opt. Soc. Am. B 9, 724 (1992)]. Although that mechanism recognizes the importance of coupling between the intrinsic and extrinsic two-level systems (TLS[sub int],TLS[sub ext]) of the chromophore/glass system and diffusion of excess free volume triggered by optical excitation, it does not adequately account for the effects of multiple excitations of redshifted (relative to the burn frequency ω[sub B]) preburn and antihole sites. The results show that multiple excitations ultimately lead to the entire antihole being blueshifted. A "second channel" of hole burning becomes apparent at sufficiently high burn fluences. A model for t... [ABSTRACT FROM AUTHOR]

Comments on an article, entitled `A comment on dielectric hole burning,' published in the volume 111 issue of the `Journal of Chemical Physics'. Application of the nonresonant spectral hole burning to study the dynamic heterogeneity of supercooled liquids.