Spectral Hole Burning Spectroscopy Research Articles

Evidence of Simultaneous Spectral Hole Burning Involving Two Tiers of the Protein Energy Landscape in Cytochrome b6f.

Cytochrome b6f, with one chlorophyll molecule per protein monomer, is a simple model system whose studies can help achieve a better understanding of nonphotochemical spectral hole burning (NPHB) and single-complex spectroscopy results obtained in more complicated photosynthetic chlorophyll-protein complexes. We are reporting new data and proposing an alternative explanation for spectral dynamics that was recently observed in cytochrome b6f using NPHB. The relevant distribution of the tunneling parameter λ is a superposition of two components that are nearly degenerate in terms of the resultant NPHB yield and represent two tiers of the energy landscape responsible for NPHB. These two components likely burn competitively; we present the first demonstration of modeling a competitive NPHB process. Similar values of the NPHB yield result from distinctly different combinations of barrier heights, shifts along the generalized coordinate d, and/or masses of the entities involved in conformational changes m, with md2 parameter different by a factor of 2.7. Consequently, in cytochrome b6f, the first (at least) 10 h of fixed-temperature recovery preferentially probe different components of the barrier- and λ-distributions encoded into the spectral holes than thermocycling experiments. Both components most likely represent dynamics of the protein and not of the surrounding buffer/glycerol glass.

Photoluminescence excitation and spectral hole burning spectroscopy of silicon vacancy centers in diamond

Silicon-vacancy (SiV) centers in diamond are promising systems for quantum information applications due to their bright single photon emission and optically accessible spin states. Furthermore, SiV centers in low-strain diamond are insensitive to pertubations of the dielectric environment, i.e. they show very weak spectral diffusion. This property renders ensembles of SiV centers interesting for sensing applications. We here report on photoluminescence excitation (PLE) spectroscopy on an SiV ensemble in a low strain, CVD-grown high quality diamond layer, where we measure the fine structure with high resolution and obtain the linewidths and splittings of the SiV centers. We investigate the temperature dependence of the width and position of the fine structure peaks. Our measurements reveal linewidths of about 10 GHz as compared to a lifetime limited width on the order of 0.1 GHz. This difference arises from the inhomogeneous broadening of the transitions caused by residual strain. To overcome inhomogeneous broadening we use spectral hole burning spectroscopy which enables us to measure a nearly lifetime limited homogeneous linewidth of 279 MHz. Furthermore, we demonstrate evidence of coherent interaction in the system by driving a $\Lambda$-scheme. Additional measurements on single emitters created by ion implantation confirm the homogeneous linewidths seen in the spectral hole burning experiments and relate the ground state splitting to the decoherence rate.

Monte Carlo Modeling of Spectral Diffusion Employing Multiwell Protein Energy Landscapes: Application to Pigment-Protein Complexes Involved in Photosynthesis.

We are reporting development and initial applications of the light-induced and thermally induced spectral diffusion modeling software, covering nonphotochemical spectral hole burning (NPHB), hole recovery, and single-molecule spectroscopy and involving random generation of the multiwell protein energy landscapes. The model includes tunneling and activated barrier-hopping in both ground and excited states of a protein-chromophore system. Evolution of such a system is predicted by solving the system of rate equations. Using the barrier parameters from the range typical for the energy landscapes of the pigment-protein complexes involved in photosynthesis, we (a) show that realistic cooling of the sample must result in proteins quite far from thermodynamic equilibrium, (b) demonstrate hole evolution in the cases of burning, fixed-temperature recovery and thermocycling that mostly agrees with the experiment and modeling based on the NPHB master equation, and (c) explore the effects of different protein energy landscapes on the antihole shape. Introducing the multiwell energy landscapes and starting the hole burning experiments in realistic nonequilibrium conditions are not sufficient to explain all experimental observations even qualitatively. Therefore, for instance, one is required to invoke the modified NPHB mechanism where a complex interplay of several small conformational changes is poising the energy landscape of the pigment-protein system for downhill tunneling.

Two-photon spectral hole burning spectroscopy of InAs/GaAs quantum dots

Femtosecond spectral hole burning experiments were performed on InAs/GaAs quantum dots to investigate the influence of high excitation intensities. The observation of additional spectral holes, as well as distinct absorption line broadening are both attributed to two-photon absorption processes. These spectral holes can be unambiguously assigned to degenerate two-photon biexciton creation, whereas the absorption line broadening is a direct result of Coulomb renormalization, initiated by carriers created through two-photon absorption in the surrounding GaAs crystal matrix and the InAs wetting layer.

New all-optical method for measuring molecular permanent dipole moment difference using two-photon absorption spectroscopy

Stark effect, in combination with spectral hole burning and single-molecule spectroscopy, has been a fruitful technique to study permanent electric dipole moment of molecules in condensed phase. However, because measuring Stark shifts relies on external fields and narrow line- or hole-widths, the applicability of this method at ambient conditions required by most biological systems has remained limited. Here we demonstrate a new all-optical method for measuring the molecular dipole moment difference between ground and excited states using two-photon absorption (2PA) spectroscopy. We show that the value and orientation of the static dipole moment difference can be determined from the corresponding absolute 2PA cross-section. We use this new method to determine for the first time the strength of local electric field E loc =0.1–1.0×10 8 V/cm inside beta-barrel of Fruit series of red fluorescent proteins. Because our method does not rely on external field and is applicable in liquid solutions, it is well suited for the study of biological systems.

Spectroscopic investigations of a [formula omitted] waveguide for photon-echo quantum memory

We report the fabrication and characterization of a Ti 4 + : Tm 3 + : LiNbO 3 optical waveguide in view of photon-echo quantum memory applications. Specifically, we investigated room- and cryogenic-temperature properties of the waveguide, and the Tm 3 + ions, via absorption, spectral hole burning, photon echo, and Stark spectroscopy. For the Tm 3 + ions, we found radiative lifetimes of 82 μ s and 2.4 ms for the H 4 3 and F 4 3 levels, respectively, and a 44% branching ratio from the H 4 3 to the F 4 3 level. We also measured an optical coherence time of 1.6 μ s for the H 6 3 ↔ H 4 3 , 795 nm wavelength transition, and investigated the limitation of spectral diffusion to spectral hole burning. Upon application of magnetic fields of a few hundred Gauss, we observed persistent spectral holes with lifetimes up to seconds. Furthermore, we measured a linear Stark shift of 25 kHz cm / V . Our results are promising for integrated, electro-optical, waveguide quantum memory for photons.

Hydrogen Bond Fluctuations of the Hydration Shell of the Bromide Anion

We study the hydrogen bond dynamics of solutions of LiBr and NaBr in isotopically diluted water (2% HDO:D2O) with femtosecond spectral hole-burning spectroscopy. We study the frequency fluctuations of the O-H stretch vibrations of the HDO molecules and observe spectral dynamics with time constants of 0.8 +/- 0.1 ps and 4.3 +/- 0.3 ps. The slow process we assign to the hydrogen bond fluctuations of the O-H...Br- hydrogen bonds of the hydration shell of the Br- anion. We find that the time scale of the hydrogen bond fluctuations of the hydration shell of Br- is independent of the nature of the cation and the concentration.

Coherent control of ground state excitons in the nonlinear regime within an ensemble of self‐assembled InAs quantum dots

AbstractIn this work femtosecond spectral hole burning spectroscopy is used to resonantly excite ground state excitons in an ensemble of self‐assembled InAs/GaAs quantum dots with a strong pump pulse. Two fundamental coherent nonlinear effects are observed with the aid of the intrinsic time‐ and frequency resolution of the setup: The low temperature Rabi oscillation of the two‐level system associated with the excitonic ground state transition and the observation of two‐photon absorption in the surrounding GaAs crystal matrix. The emergence of the latter effect also infers the existence of charged excitons in the nominally undoped QD sample, backed up by the observation of additional spectral holes next to the excitonic transitions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Zeeman-level lifetimes inEr3+:Y2SiO5

We present measurements of Zeeman-level population lifetimes in ${\text{Er}}^{3+}:{\text{Y}}_{2}{\text{SiO}}_{5}$ at low magnetic fields and low temperatures. Using spectral hole burning spectroscopy, we investigate the dynamics and temperature dependence of the hole structure due to the Zeeman interaction. Evidence for population storage in Zeeman levels with lifetimes of up to 130 ms is found in the form of long-lived spectral holes and antiholes. We also observe that a subset of the erbium ions exhibit very long-lived holes with lifetimes as long as 60 s at 2.8 K.

Femtosecond Spectral Hole Burning Spectroscopy as a Probe of Exciton Dynamics in Quantum Dots

We present measurements of the dynamics of photoexcited excitons inan ensemble of InAs/GaAs self-assembled quantum dots using a femtosec-ond spectral hole burning technique. We use this technique to examine theexciton spin relaxation and the line shape of optical transitions in the dots.PACS numbers: 73.21.La, 78.47.{p, 78.67.Hc

Confined Acoustic Vibration Modes in CuBr Quantum Dots

Confined acoustic phonons in CuBr quantum dots (QDs) are studied for the first time using coherent phonon measurements and persistent spectral hole burning (PSHB) spectroscopy. A size-dependent damped oscillation with sub-THz frequency is observed in femtosecond pump-probe measurements of CuBr QDs in glass. Similarly, a size-dependent acoustic phonon hole with an energy shift of 1–2 meV is observed in PSHB spectra of CuBr QDs in glass and NaBr crystals. The energies of the confined acoustic phonons obtained by the two methods are in good agreement with each other. In addition, there is no difference in size-dependence between the glass matrix and NaBr matrix. The size dependence of acoustic phonons can be explained well as low frequency vibrational modes of CuBr QDs based on an elastic sphere model. The dominant mode is assigned to the l =2 spheroidal mode, while the l =0 mode is also observed.

Hole burning and single-molecule spectroscopy of terrylene in incommensurate biphenyl

Techniques of spectral hole burning and single-molecule spectroscopy have been used to study thin films of polycrystalline terrylene-doped biphenyl at temperatures between 1.7 and 2.2 K. A very wide range of probabilities of photoinduced spectral transitions of terrylene molecules are indicated by the strong non-exponentiality of non-photochemical hole burning processes and observation of some extremely stable single-molecule lines. Broad distribution of single-molecule linewidths as well as obvious disagreement between their average value and the corresponding holewidth also demonstrate a large variety of spectral behaviour of terrylene impurity molecules. We attribute these effects to spatial variations of local environment of terrylene molecules in an incommensurate matrix of biphenyl.

Longitudinal optical phonons in the excited state of CuBr quantum dots

The size dependence of the longitudinal optical (LO) phonons in the excited state of CuBr quantum dots (QD's) in glass and NaBr crystals in the intermediate confinement regime was studied by means of persistent spectral hole burning spectroscopy. The phonon-exciton coupled states were clearly observed at a photon energy of about 2.993 eV when the LO phonon energy is close to the energy difference between the ground $1S$ and excited $1P$ states of CuBr QD's in glass. The energies of the LO phonons observed in smaller CuBr QD's in glass and NaBr crystals were determined to be about 18.6 and 17.6 meV, respectively, which are smaller than that of LO phonons in the bulk CuBr material. The energy softening of the LO phonons was explained in terms of the phonon renormalization.

Methyl torsional potentials of rotational isomers of m-methylanisole studied by spectral hole-burning spectroscopy

Laser-induced fluorescence (LIF) excitation spectra of m-methylanisole in a supersonic jet were measured. Two series of progressions were observed in the spectrum, originating at 36048 and 36115 cm −1, which were successfully assigned to the transitions to the methyl internal rotational vibronic levels of the two isomers, i.e. cis and trans isomers, with the aid of hole-burning spectrum measurements and quantum-chemical calculations. The progression for the trans isomer was observed up to the 6a 1 band, while only the 3a 1 band in addition to the 0a 1 and 1e bands was observed for the cis isomer. This finding can be explained by the conformational change upon the electronic excitation; the 60° rotation of the methyl torsional angle takes place for the trans isomer but not for the cis isomer.

Single-cell nonphotochemical hole burning of ovarian surface epithelial carcinoma and normal cells.

Persistent spectral nonphotochemical hole-burning (NPHB) spectroscopy has recently been applied to dye molecules in cells. The sensitivity of NPHB to the nanoenvironment of the probe is well established. It has been shown that NPHB applied to bulk suspensions of cultured human cells can distinguish between normal and cancer cells. Thus, NPHB has potential as a diagnostic cancer tool. For this reason, the methodology is referred to as hole-burning imaging, by analogy with MRI. The optical dephasing time (T(2)) of the dye in hole-burning image replaces the proton T(1) relaxation time in MRI. In addition to the T(2) mode of operation, there are four other modes including measurement of the spectral hole growth kinetics (HGK). Reported here is that the selectivity and sensitivity of NPHB operating in the HGK mode allow for distinction between normal and carcinoma cells at the single-cell level. The ovarian cell lines are ovarian surface epithelial cells with temperature-sensitive large T antigens (analogously normal) and ovarian surface epithelial carcinoma (OV167) cells. The mitochondrial specific dye used was rhodamine 800 (Molecular Probes). This carbocationic dye is highly specific for the outer and inner membranes of mitochondria. In line with the results for bulk suspensions of the two cell lines, the hole-burning efficiency for OV167 cells was found to be significantly higher than that for normal cells. Theoretical analysis of the HGK data leads to the conclusion that the degree of structural heterogeneity for the probe-host configurations in OV167 cells is lower than in the normal cells. Possible reasons for this are given.

High-resolution laser spectroscopy of rare-earth doped insulators: a personal perspective

I offer some reflections on the past three decades of high-resolution spectroscopy of rare-earth ions in solids which was ushered in by the development of tunable lasers in the mid 1970s. A brief review is given of some of the accomplishments in the area of spectral hole-burning and coherent transient spectroscopy, emphasizing work with which the author has been associated. Spectral hole-burning has been characterized by a richness of mechanisms. These include population storage in nuclear-spin and electron-spin Zeeman sub-levels, hyperfine and superhyperfine levels and metastable optical levels with corresponding hole lifetimes from many hours to microseconds. In addition, persistent hole-burning has been seen in disordered materials and in those showing photo-ionization or photo-chemistry following excitation into zero-phonon lines. This has made hole-burning a generally useful technique for the measurement of magnetic and electric dipole moments, hyperfine interactions, spin relaxation and thermally induced line-broadening. Photon-echoes have proven to be the prime source of coherence-time information and coherence times as long as several milliseconds corresponding to optical resonance widths of less than 100 Hz have been reported. Tables summarizing these results and providing references to original work are included.

Internal Rotation and Intermolecular Vibrations of the Phenol−Methanol Cluster: A Comparison of Spectroscopic Results and Ab Initio Theory

The vibronic spectra of five deuterated species of the binary phenol−methanol cluster are compared to the intermolecular vibrational frequencies of an ab initio-based normal-mode analysis. Isotopomers with equal mass could be distinguished experimentally using spectral hole-burning spectroscopy. The vibronic bands of phenol−methanol are split into A and E components because of the internal rotation of the methyl group. This torsional splitting is increased for three of the intermolecular vibrations because of coupling to the large-amplitude motion. Guided by comparison to an ab initio normal-mode analysis and by the torsional splitting of some of the vibronic bands, a complete intermolecular vibrational assignment for the phenol−methanol cluster is presented.

All-solid-state, tunable, single-frequency source of yellow light for high-resolution spectroscopy

We demonstrate a cw doubly resonant optical parametric oscillator that is frequency doubled in an external resonant cavity to the visible spectral range. We obtained single-frequency radiation in the range 565-590 nm with as much as 3.8 mW of power, which is continuously tunable over an 18-GHz range and step tunable over 160 GHz. The source is well suited for high-resolution spectroscopy in the visible region. As a demonstration, we performed persistent hyperfine spectral hole-burning spectroscopy of Eu(3+): Y(2)SiO(5) . Reliable operation of the source permitted studies of the hole's lifetime over several hours.

Local proton dynamics in perovskite-type protonic conductors by spectral hole burning spectroscopy

Local proton dynamics in several kinds of perovskite-type high-temperature protonic conductors were investigated by spectral hole burning spectroscopy. Spectral holes based on light-induced protonic motion were observed. By applying a temperature-cycling technique, the potential barriers for local protonic motion, which is responsible for hole burning, were estimated. The values were several times lower than the activation energies obtained by electric conductivity measurements. The relationship between elementally protonic motion and long-range conduction mechanism is discussed based on these results.

Exciton-phonon coupled states in CuCl quantum cubes

The size dependence of excitonic states and vibrational modes in CuCl cubic quantum dots embedded in NaCl crystals was studied by means of site-selective persistent spectral hole burning spectroscopy. It is shown that the interaction of the longitudinal optical (LO) phonon with the exciton results in the formation of coupled exciton-phonon modes when the energy of the LO phonon approaches the energy spacings between the ground and excited states of the exciton. The energy anticrossings of the LO phonon modes with two higher optically allowed excited states of the exciton in CuCl QD's were clearly observed at confinement energies of about 10 and 6 meV, respectively. In addition, the linewidth of the LO phonon sideband in CuCl QD's in NaCl crystals was found to increase abruptly from 0.3 meV to about 1.2 meV at a confinement energy of about 23 meV, which appears to result from the exciton-phonon mixing of the LO phonon mode with the first excited state of the exciton. The experimental results are qualitatively understood by the LO phonon renormalization theory.