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A detailed description is given of how the liquid water content (LWC) and the ice water content (IWC) can be determined accurately and absolutely from the measured water Raman spectra of clouds. All instrumental and spectroscopic parameters that affect the accuracy of the water-content measurement are discussed and quantified; specifically, these are the effective absolute differential Raman backscattering cross section of water vapor , and the molecular Raman backscattering efficiencies ηliq and ηice of liquid and frozen microparticles, respectively. The latter two are determined following rigorous theoretical approaches combined with Raman Lidar for Atmospheric Moisture Sensing (RAMSES) measurements. For ηice, this includes a new experimental method that assumes continuity of the number of water molecules across the vertical extent of the melting layer. Examples of water-content measurements are presented, including supercooled liquid-water clouds and melting layers. Error sources are discussed; one effect that stands out is interfering fluorescence by aerosols. Aerosol effects and calibration issues are the main reasons why spectral Raman measurements are required for quantitative measurements of LWC and IWC. The presented study lays the foundation for cloud microphysical investigations and for the evaluation of cloud models or the cloud data products of other instruments. As a first application, IWC retrieval methods are evaluated that are based on either lidar extinction or radar reflectivity measurements. While the lidar-based retrievals show unsatisfactory agreement with the RAMSES IWC measurements, the radar-based IWC retrieval which is used in the Cloudnet project performs reasonably well. On average, retrieved IWC agrees within 20% to 30% (dry bias) with measured IWC.

This short review begins with a brief introductory summary of luminescence nanothermometry. Current applications of luminescence nanothermometry are introduced in biological contexts. Then, theoretical bases of the “temperature” that luminescence nanothermometry determines are discussed. This argument is followed by the 105 gap issue between simple calculation and the measurements reported in literatures. The gap issue is challenged by recent literatures reporting single-cell thermometry using non-luminescent probes, as well as a report that determines the thermal conductivity of a single lipid bilayer using luminescence nanothermometry. In the end, we argue if we can be optimistic about the solution of the 105 gap issue.

Nanodiamonds containing luminescent point defects are widely explored for applications in quantum bio-sensing such as nanoscale magnetometry, thermometry, and electrometry. A key challenge in the development of such applications is a large variation in fluorescence properties observed between particles, even when obtained from the same batch or nominally identical fabrication processes. By theoretically modelling the emission of nitrogen-vacancy colour centres in spherical nanoparticles, we are able to show that the fluorescence spectrum varies with the exact position of the emitter within the nanoparticle, with noticeable effects seen when the diamond radius, $a$, is larger than around 100 nm, and significantly modified fluorescence profiles found for larger particles when $a=200$ nm and $a=300$ nm, while negligible effects below $a=100$ nm. These results show that the reproducible geometry of point defect position within narrowly sized batch of diamond crystals is necessary for controlling the emission properties. Our results are useful for understanding the extent to which nanodiamonds can be optimised for bio-sensing applications.

In this paper, for the first time, tuned near-zero-index materials are used in a structure for the long-distance projection of very closely spaced objects with subwavelength separation. Near-zero-index materials have never been used for subwavelength projection/imaging. The proposed novel structure is composed of a two-layer slab that can project two slits with a subwavelength separation distance to a long distance without diverged/converged interference of the two imaged waves. The two-layer slab consists of a thin double-near-zero (DNZ) slab with an obtained tuned index of 0.05 and thickness of 0.04λ0 coupled with a high-index dielectric slab with specific thicknesses. Through a parametric study, the non-zero index of the DNZ layer is tuned to create a clear image when it is coupled with the high-index dielectric layer. The minimum size for the aperture of the proposed two-layer slab is 2λ0 to provide a clear projection of the two slits. The space between the slits is λ0/8, which is five times beyond the diffraction limit. It is shown that, through the conventional methods (e.g., only with high-index dielectric slabs, uncoupled with a DNZ layer), it is impossible to clearly project slits at a large distance (~λ0) due to the diffraction limit. An analytical analysis, as well as numerical results in a finite-element-based simulator, confirm the function of the proposed structure.

Fluorescence excitation spectra of single terrylene molecules in transparent naphthalene and polyethylene matrices at ultralow (30–100 mK) temperatures have been studied under the conditions where the widths of zero-phonon spectral lines are determined only by the lifetime T1 of the excited electronic state. The experimentally observed dispersion of T1 values for identical molecules is attributed to local field effects, which are responsible for the dependence of T1 on the effective value of refractive index n of the matrix, which is characteristic of the localization region of each molecule. It has been shown that the dependence T1(n) for ensembles of point emitters in organic matrices is satisfactorily explained within the model of a “virtual cavity” around the emitter inside a continuous medium, as well as within the developed quantum kinetic approach including various contributions of the local environment to the lifetime T1. The recalculation of average T1 values to the corresponding n values with the use of the expressions obtained for T1(n) has shown that the difference of the calculated refractive indices of naphthalene and polyethylene from the well-known tabulated n values is less than 1%.

Newly made hybrid nanosensors measured thermal conductivity in cells to be about one-sixth of that in water., Understanding heat dissipation processes at nanoscale during cellular thermogenesis is essential to clarify the relationships between the heat and biological processes in cells and organisms. A key parameter determining the heat flux inside a cell is the local thermal conductivity, a factor poorly investigated both experimentally and theoretically. Here, using a nanoheater/nanothermometer hybrid made of a polydopamine encapsulating a fluorescent nanodiamond, we measured the intracellular thermal conductivities of HeLa and MCF-7 cells with a spatial resolution of about 200 nm. The mean values determined in these two cell lines are both 0.11 ± 0.04 W m−1 K−1, which is significantly smaller than that of water. Bayesian analysis of the data suggests there is a variation of the thermal conductivity within a cell. These results make the biological impact of transient temperature spikes in a cell much more feasible, and suggest that cells may use heat flux for short-distance thermal signaling.

Understanding heat dissipation processes at nanoscale during cellular thermogenesis is essential to clarify the relationships between the heat and biological processes in cells and organisms. A key parameter determining the heat flux inside a cell is the local thermal conductivity, a factor poorly investigated both experimentally and theoretically. Here, using a nanoheater/nanothermometer hybrid based on a polydopamine shell encapsulating a fluorescent diamond nanocrystal, we measured the intracellular thermal conductivity of HeLa cell with a spatial resolution of about 200 nm. Its mean value of 0.11 Wm-1K-1 determined for the first time is significantly smaller than that of water. Bayesian analysis of the data strongly supports the existence of variation of the intracellular thermal conductivity of about 40%. These results present a major milestone towards understanding the intracellular heat transfer phenomena at nanoscale.

We have produced two types of synthetic nanodiamonds Si- and Si,P-doped and have characterized the thermal susceptibilities of the spectral band of silicon-vacancy (SiV-) centers at approximately 740 nm in each case. The covered temperature range from 295 to 350 K is of interest for thermometry in biological systems. Comparison of the relative brightness of the Si- and Si,P-doped crystals shows that phosphorous significantly increases average concentration and homogeneity of distribution of SiV- centers in nanodiamonds. Moreover, linear dependence on temperature of the zero-phonon line width in Si-doped crystals is 0.061(2) nm K-1 but is 0.047(3) nm K-1, about 35% smaller in Si,P-doped nanodiamonds. This proves control of SiV- properties with additional chemical doping and close proximity of Si and P atoms.

We have produced two types of synthetic nanodiamonds Si- and Si,P-doped and have characterized the thermal susceptibilities of the spectral band of silicon-vacancy (SiV

A theoretical framework is presented that permits investigations of the relation between inelastic backscattering from microparticles and bulk samples of Raman-active materials. It is based on the Lorentz reciprocity theorem and no fundamental restrictions concerning the microparticle shape apply. The approach provides a simple and intuitive explanation for the enhancement of the differential backscattering cross-section in particles in comparison to bulk. The enhancement factor for scattering of water droplets in the diameter range from 0 to 60 mu m (vitally important for the a priori measurement of liquid water content of warm clouds with spectroscopic Raman lidars) is about a factor of 1.2-1.6 larger (depending on the size of the sphere) than an earlier study has shown. The numerical calculations are extended to 1000 mu m and demonstrate that dispersion of the refractive index of water becomes an important factor for spheres larger than 100 mu m. The physics of the oscillatory phenomena predicted by the simulations is explained. (C) 2018 Elsevier Ltd. All rights reserved.

Functionalized diamond nanocrystals persistently expand their use for sensing and labeling in a biological context. The surface of such crystals modified chemically adds additional modality to such applications. In this Perspective, we discuss mainly applications in nanothermometry but begin with a brief general introduction of fluorescent nanodiamonds. Then we consider temperature at the sub-cellular environment, explain the working principle of fluorescent nanodiamonds as temperature probes, and demonstrate their biological applications from the literature. The application of nanohybrids (such as heater-thermometer hybrids built within a single nanoparticle) in biological cells will be covered with more details. We summarize recent results of intracellular measurements to estimate that 0.1 nJ of heat released in a cellular hot spot of 1-μm radius can produce a 1-K temperature rise lasting for about 50 μs and repeatable approximately every 2 ms. Our view on the reason for limitations in biological applications of nanodiamonds concludes the review.

Measurements of Raman backscattering spectra between -15 C-omicron and 22 C-omicron in liquid water (including its supercooled state) and in polycrystalline ice (-35 C-omicron to 0 C-omicron) at two excitation wavelengths (407 and 532 nm) are presented. It is found that the spectrum-integrated backscattering cross-section of the 3400 cm(-1) band is about 1.2 times larger for ice in comparison to liquid water. The excitation-wavelength dependence of the cross-section in ice is very close to that in water. A discontinuous change of the spectrum is observed upon phase transition at 0 C-omicron. The results are applicable to preliminary calibration of lidar systems designed for water content surveys in the atmosphere. (C) 2017 Elsevier Ltd. All rights reserved.

This paper reviews applications of diamonds for sensing of magnetic and electrical fields, pressure and temperature. Considerable attention is focussed on the interaction of spins with static and oscillating magnetic fields as well as applications of such fields to spin control. A particular focus is on the spin of nitrogen-vacancy centers. Electron-spin microwave resonances play a central role in the ultra-sensitive metrology on the nanoscale, but pure optical methods are also considered in this review.

Nanoscale thermometry is paramount to study primary processes of heat transfer in solids and is a subject of hot debate in cell biology. Here we report ultrafast temperature sensing using all-optical thermometry, exploiting synthetic nanodiamonds with silicon-vacancy (SiV) centers embedded at a high concentration. Using multiparametric analysis of photoluminescence (PL) of these centers, we have experimentally achieved an intrinsic noise floor of about 13 mK Hz , which is a 1000-fold increase in the readout speed in comparison to the current record values demonstrated with all-optical methods of comparable spatial-resolution and precision. Our thermometers are smaller than 250 nm across but can detect a 0.4 °C change of temperature in a measurement taking only 0.001 s. The exceptional sensitivity and simplicity of these thermometers enable a wide range of applications such as temperature monitoring and mapping within intracellular regions and in state-of-the-art solid-state electronic nanodevices.

Modern image detectors with exceptionally low readout noise of about one electron ( e − ) per pixel allow for applications with ultra-low levels of light intensity. In this Letter, we report a property of scientific CMOS detectors that makes accurate spectroscopy at ultra-low levels of illumination depending on a thorough calibration procedure. Our results reveal that pixel sensitivity to light may have significant nonlinearity at accumulation levels smaller than 50 e − per pixel. The sensitivity decreases by a factor of ∼ 0.7 at an accumulation level of ∼ 1 e − per pixel and photon detection rate of about 170 Hz. We demonstrate that the nature of this nonlinearity might be quite complicated: the photoelectric response of a pixel depends on both the number of accumulated electrons and the detection count rate (at rates larger than 250 Hz).

We have synthesized novel composite particles made of single-domain nanomagnets chemically bound to nanocrystals of diamond. Optically detected magnetic resonance spectra of nitrogen-vacancy centers in diamond allowed us to estimate the magnetic field of the nanomagnets and to observe the saturation of their magnetization when an external field of a few tens of mT has been applied. The saturation effect is in agreement with the size of the domains measured using transmission electron microscopy and a simple model of magnetization.

The paper describes application of diamond nano crystals to research on dynamic processes in small (less than 1 mm across) evaporating droplets deposited on a solid substrate. Such droplets are used as a model system for testing proposed bio applications of nitrogen-vacancy centers in diamond. We demonstrate that a high spatial resolution of our methods reveals unexpected features of the evaporation and fluid mechanics in such droplets.

The negatively-charged nitrogen-vacancy (NV) center in diamond is at the frontier of quantum nano-metrology and bio-sensing. Recent attention has focused on the application of high-sensitivity thermometry using the spin resonances of NV centers in nano-diamond to sub-cellular biological and biomedical research. Here, we report a comprehensive investigation of the thermal properties of the center's spin resonances and demonstrate an alternate all-optical NV thermometry technique that exploits the temperature dependence of the center's optical Debye-Waller factor., 22 pages, 5 figures

Spectral diffusion of the emission line of single colloidal nanocrystals is generally regarded as a random process. Here, we show that each new spectral position has a finite memory of previous spectral positions, as evidenced by persistent anticorrelations in time series of spectral jumps. The anticorrelation indicates that there is an enhanced probability of the charge distribution around the nanocrystal returning to a previous configuration. We show both statistically and directly that this memory manifests as an observable spontaneous "relaxation" in the absence of a pump laser, so that spectral diffusion progresses in a manner of "two steps forward and one step back".

In this report, we present a detection scheme that can be used to measure the absorption cross-section of the Nitrogen Vacancy (NV) centre, along with the results of an experimental implementation of this method. We also demonstrate how we quantify the number of NV centres in a crystal by calculating the collection efficiency of our apparatus. We find that the absorption cross-section for 532 nm excitation, averaged over the possible orientations of the transition dipole moments is ( 0.95 ± 0.25 ) × 10 - 16 cm 2 . This level of accuracy has not been achieved in previous investigations.

In this work we quantify and characterise the effects of air-oxidation on nitrogen-vacancy defect luminescence in both high-temperature-high-pressure and detonation synthesized nanodiamonds using Raman and luminescence spectroscopies. We find that oxidation treatments result in an increased nitrogen-vacancy centre excited state lifetime from 13 ns to 25 ns and in 5-nm diamonds the intensity of this luminescence increases by at least 5-fold. At the same time, in 5-nm diamonds, short lived surface-defect related luminescence is reduced by 10-fold. Furthermore we find that air oxidation reduces the sp 2 and disordered carbon fraction of nanodiamonds by up to 5-fold in 5-nm nanodiamonds. Based on these results, the authors suggest that the disordered-carbon and graphite shell of 5-nm nanodiamonds quenches nitrogen-vacancy luminescence, and that this quenching can be partially reduced by surface oxidation. These findings provide useful insights into the role of the graphite and disordered carbon shell in quenching luminescence, and have implications for the applicability of 5-nm nanodiamonds to bio- and quantum physics applications.

A general method for counting of obscure events in presence of detection noise is presented. The method combines the measurement data with additional information about the system under investigation to improve the measurement accuracy with the help of probability theory. As an example, we apply the method to the case of counting molecules in a microfluidic device and show in simulations that the accuracy is always better than for a thresholding approach. As a second example, we show how it can be used for photon counting at high count rates with an electron multiplying CCD (EMCCD) camera.

We propose a new methodology for probing transport of just one electron, a process of great importance both in nature and in artificial devices. Our idea for locating a single electron is analogues to the conventional GPS where signals from several satellites are used to locate a macro object. Using fluorescent molecules as tiny sensors, it is possible to determine 3D displacement vector of an electron.

We report on the first demonstration of nanodiamond (ND) as a scattering optical label in a biological environment. NDs were efficiently transfected into cells using cationic liposomes, and imaged using differential interference and Hoffman modulation ‘space’ contrast microscopy techniques. We have shown that 55 nm NDs are biologically inert and produce a bright signal compared to the cell background. ND as a scattering label presents the possibility for extended biological imaging with relatively little thermal or biochemical perturbations due to the optical transparency and biologically inert nature of diamond.

Applications of negatively charged nitrogen-vacancy center in diamond exploit the center's unique optical and spin properties, which at ambient temperature, are predominately governed by electron-phonon interactions. Here, we investigate these interactions at ambient and elevated temperatures by observing the motional narrowing of the center's excited state spin resonances. We determine that the center's Jahn-Teller dynamics are much slower than currently believed and identify the vital role of symmetric phonon modes. Our results have pronounced implications for center's diverse applications (including quantum technology) and for understanding its fundamental properties., Comment: 5 pages, 4 figures

Electron-multiplying charge coupled devices promise to revolutionize ultrasensitive optical imaging. The authors present a simple methodology allowing reliable measurement of camera characteristics and statistics of single-electron events, compare the measurements to a simple theoretical model, and report camera performance in a truly photon-counting regime that eliminates the excess noise related to fluctuations of the multiplication gain.

Optical Bloch equations are widely used for describing dynamics in a system consisting molecules, electromagnetic waves, and a thermal bath. We analyze applicability of these equations to a single molecule imbedded in a solid matrix. Classical Bloch equations and the limits of their applicability are derived from more general master equations. Simple and intuitively appealing picture based on stochastic Bloch equations shows that at low temperatures, contrary to common believes, a strong driving field can not only suppress but can also increase decay rates of Rabi oscillations. A physical system where predicted effects can be observed experimentally is suggested.

A straightforward derivation of relativistic expressions for the mechanical momentum, kinetic and total energies, and mass-energy equivalence (including potential energy) which does not require any knowledge of the energy-momentum relation for electromagnetic waves or consideration of elastic collisions, but is directly based on Newton's second law and Lorentz's transformations, is presented in this paper. The existence of an invariant force is shown to be important for the validity of the relativistic mechanics.

Fluorescence of single molecules coupled to a pseudo localized vibration (PLV) and a thermal bath is studied both experimentally and theoretically. The coupled system molecule-PLV is described by master equations which are tested in an experiment where a shape of an excitation spectral line of a single molecule is accurately measured over six orders of magnitude of the exciting laser power. Significant deviations from the predictions of the standard Bloch equations are found but the master equations work very well. The role of critical parameters-the correlation time of the bath, the Rabi oscillation period, and the coupling constant between the bath and the molecule is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Absorption of single molecules is considered as a special case of an interference effect. Different schemes of interference measurements, which are more suitable for single molecules, are described. Advantages and disadvantages of absorption detection relative to emission (luminescence) detection are analyzed. A great attention is paid to a comparison of signal-to-noise ratios for the two types of measurements.

A novel technique of saturation spectroscopy is applied to study the individual vibronic spectra of single impurity molecules embedded in a low-temperature solid matrix. Homogeneous linewidths and vibrational frequencies for two lower vibronic levels of the excited electronic state S1 are determined for several terrylene single molecules in a naphthalene crystal, which indicates a noticeable distribution of these parameters. A certain correlation can be pointed out between vibrational frequency and a purely electronic transition frequency of a terrylene molecule.

The paper briefly overviews a master equation theory for the case of a single pseudolocal vibration interacting with an electronic molecular transition, a phonon bath, and laser irradiation. The theory is valid for a broad range of laser powers. At low laser powers it was compared to sudden-jump model. Qualitatively, both theories predict that in addition to the conventional Lorentzian, the line consists of a dispersive component in the core region and a side band. Quantitatively, the sudden jump model is applicable only if the vibration–phonon coupling is independent of the electronic wave functions. An interesting property of the complex line was found at strong excitation. In this case the line first behaves in a fashion intermediate to the saturation behavior of homogeneously and inhomogeneously broadened spectra. But as the laser intensity is growing, the interaction with optical field “suppress” the dephasing caused by the interaction with the matrix and the line becomes a Lorentzian.

We present a progress report on investigations of dye-doped microstructures. Motivated by the effect that a confined sample volume may have upon the optical linewidths of dye doped into a small sample, we studied polystyrene microspheres (300 nm in diameter) doped with terrylene. Terrylene doped into polystyrene microspheres has a quantum efficiency of hole burning of similar to 10(-6). The hole burning also has a very efficient light-induced back reaction. The temperature dependence of the hole width in the microsphere sample has a greater slope as compared to the bulk sample indicating a higher concentration of two level systems associated with the high surface area to volume ratio. The microsphere sample also shows a plateau in the hole widths at low (< 200 mK) temperature. The narrowest hole which could be burnt at these temperatures was similar to 350 MHz wide. This width is considerably broader than expected from the lifetime-limited value. (C) 2001 Elsevier Science B.V. All rights reserved.

Linewidth measurements for single terrylene molecules in polyethylene at a temperature of 30 mK indicate that there is a distribution of lifetimes for the terrylene molecules with a relative standard deviation of ∼20%. An analysis of the linewidth–line area correlation shows that the variations arise from approximately equal radiative and nonradiative contributions. A simple model suggests that the distribution of radiative lifetimes in disordered media is a general effect caused by the same interactions responsible for inhomogeneous broadening. In addition to the transition frequency, the luminescence lifetime of a probe molecule can be used to study the nano-environment of the probe.

Detailed analysis is done for the case of a single pseudo local phonon interacting with an electronic molecular transition and a phonon bath. Both the sudden-jump model and the master equation formalism predict a complex optical line shape for a single-molecule embedded in a solid matrix. In addition to the conventional Lorentzian, the line consists of a dispersive component in the core region and a side band. The sudden jump model is applicable only if the vibration-phonon coupling is independent of the electronic wave functions. However if the line wings are neglected, the sudden jump model can fit experimental data even when the condition of its applicability is not fulfilled. An interesting property of the complex line was found at strong excitation. In this case the line behaves in a fashion intermediate to the homogeneously and inhomogeneously broadened spectra.

The temperature and laser-power dependent S1 ← S0 spectra of single diphenyloctatetraene molecules in n-tetradecane are investigated using one- and two-photon excitation at cryogenic temperatures. Under one-photon excitation, the single-molecule transitions shift to lower frequencies and the line widths increase with increasing temperature while the line shapes are independent of the laser power up to spectral saturation. The experimental data are consistent with the model of thermal activation of a single local phonon. Under two-photon excitation, the transitions shift linearly to lower frequencies with increasing laser power while the lines broaden only weakly. These results are discussed in terms of laser-induced ac-Stark shifts and matrix dynamics. In particular, a bottleneck effect in the thermalization of nonequilibrium phonons is supposed to play an essential role in the observed broadening and shifts. The comparison of one- and two-photon excitation spectra provides information about the processes...

The main subject of this paper is the characterization of distributions. Methods are discussed for finding characteristic parameters like the mean and width for three model distributions, namely, Gaussian, rectangular, and Lorentzian, with the greatest emphasis placed on Lorentzian distributions because of their special properties and their central role in spectroscopy. We present the errors for the characteristic parameters and discuss how to minimize them with clever experimental design and data analysis. Interpreting complex single-molecule behavior is also discussed, with an emphasis on the use of probability theory and the Bayesian approach to model selection.

Linewidth distributions for single terrylene molecules in polyethylene have been measured in the temperature range from 30 mK to 1.83 K. The temperature dependence of the average linewidth is linear over the full temperature range. Linewidth distributions were simulated using the tunneling two-level system model and compared to the data in order to extract the lifetime-limited linewidth distributions and the distributions of coupling strengths between the probe molecules and the two-level systems. Differences of the average lifetime and coupling strengths were observed for samples produced with different sample-preparation techniques.

One- and two-photon excitation spectra, as well as absorption and emission spectra of diphenyloctatetraene (DPOT) in n-alkanes are investigated at low temperatures. For DPOT in n-octane we report on the measurements of one-photon excitation and emission spectra and for DPOT in n-tetradecane (TD) on the measurements of one- and two-photon excitation spectra and emission spectra. The spectra are governed by the transitions between the electronic ground (S0) and the two lowest electronic excited singlet states (S1,S2). The interpretation is based on allowed transitions and transitions induced by the S1–S2 coupling due to Herzberg–Teller promoting modes or due to static lattice-induced distortions of DPOT. A single noncentrosymmetric site is observed for DPOT in n-octane. For DPOT in TD a centrosymmetric and a noncentrosymmetric site are reported. The analysis indicates that there is a dynamical equilibrium in the population of these two sites. The experimental data are quantitatively studied by comparison wi...

Linewidth distributions for single terrylene molecules in polyethylene have been measured in the temperature range from 30 mK to 1.83 K. The temperature dependence of the average linewidth is best described by a linear relationship over the full temperature range. At 30 mK, the linewidth distribution has a full-width at half-maximum of ∼18.6 MHz and an average linewidth of 42.8(6) MHz.

In this work, frequency trajectories for a single terrylene molecule in n-hexadecane undergoing light-induced spectral diffusion are studied in detail. The molecule was scanned over 5000 times at three different laser powers and jumped between 6 sites. Two mechanisms for the jumping are suggested and compared to the data statistically. The linewidths are also analyzed in detail. In addition, it is revealed that a correlation between the linewidth and the line area is always present in noisy data when both parameters are found using a nonlinear least-squares fit.

Despite a long history, the Raman scattering coefficient of water has so far only been measured with 10% uncertainty using a 95% confidence interval. In this paper, we present an experiment where we have achieved 1.5% uncertainty by using a low concentration of Rhodamine 6G in ethanol as a reference along with accurate consideration of polarization-related effects and the geometry of the experimental setup. We have found that the photon-to-photon Raman scattering coefficient of the OH stretching band of liquid water is (1.84±0.03)×10(-4) m(-1) when integrated over the spectral frequency range from 620 to 700 nm while the exciting laser operates at 532 nm. We have also accurately measured the depolarization ratio across this band.

The concept of “homogeneous” spectral linewidths in doped amorphous solids and some possibilities to separate the linewidth parts related to the optical dephasing and spectral diffusion (SD) are discussed. The results of the model calculations of the photon echo (PE) decay under conditions of a large dispersion of homogeneous linewidths are presented. The deviations of the PE decay from an exponential due to this dispersion are discussed. The experimental data on incoherent PE in the terrylene/polyethylene system are presented and compared with literature single molecule spectroscopy (SMS) data. It is shown that in this case the dephasing time dispersion plays an important role for the linewidth distribution in SMS. A simple method for separation of the dephasing and SD linewidths in the SMS, based on intensity saturation effects, is considered. The facilities of this method using some SMS data are demonstrated.

The luminescence saturation behavior of a single molecule whose resonance frequency is affected by a spectral diffusion has been analyzed. On the basis of the analysis a simple way of the separate determination of the diffusive spectral line broadening and a “homogeneous” linewidth (due to fast dephasing processes) of a single molecule has been proposed.