Gaussian Decomposition vs. Semiclassical Quantum Simulation: Obtaining the High-Order Derivatives of a Spectrum in the Case of Photosynthetic Pigment Optical Properties Studying.

In this paper, a procedure for obtaining undistorted high derivatives (up to the eighth order) of the optical absorption spectra of biomolecule pigments has been developed. To assess the effectiveness of the procedure, the theoretical spectra of bacteriochlorophyll , chlorophyll , spheroidene, and spheroidenone were simulated by fitting the experimental spectra using the differential evolution algorithm. The experimental spectra were also approximated using sets of Gaussians to calculate the model absorption spectra.

Electron-Beam-Pumped UVC Emitters Based on an (Al,Ga)N Material System.

Powerful emitters of ultraviolet C (UVC) light in the wavelength range of 230-280 nm are necessary for the development of effective and safe optical disinfection technologies, highly sensitive optical spectroscopy and non-line-of-sight optical communication. This review considers UVC emitters with electron-beam pumping of heterostructures with quantum wells in an (Al,Ga)N material system. The important advantages of these emitters are the absence of the critical problem of p-type doping and the possibility of achieving record (up to several tens of watts for peak values) output optical power values in the UVC range.

Gain-switched Fe:ZnSe laser pumped by a coupled-cavity Q-switched Er:ZrF fiber laser.

We report on a gain-switched operation of single-crystal Fe:ZnSe pumped by a coupled-cavity Q-switched Er:ZrF fiber laser. With this approach, we use a continuous wave Er-doped ZrF fiber laser whose cavity is coupled with the Fe:ZnSe laser cavity. A stable Q switching operation of the Er-doped fiber laser was achieved in this case and, as a result, a gain-switched operation of the Fe:ZnSe laser was obtained.

2D-GaN/AlN Multiple Quantum Disks/Quantum Well Heterostructures for High-Power Electron-Beam Pumped UVC Emitters.

This article describes GaN/AlN heterostructures for ultraviolet-C (UVC) emitters with multiple (up to 400 periods) two-dimensional (2D)-quantum disk/quantum well structures with the same GaN nominal thicknesses of 1.5 and 16 ML-thick AlN barrier layers, which were grown by plasma-assisted molecular-beam epitaxy in a wide range of gallium and activated nitrogen flux ratios (Ga/N*) on -sapphire substrates. An increase in the Ga/N* ratio from 1.

Intracavity absorption spectroscopy of HCl isotopes, HO, CH, CH, and CH in the 3.1-3.4 µm spectral range using a Cr:CdSe laser.

We demonstrate the first application of a Cr:CdSe laser for highly-sensitive multicomponent intracavity absorption spectroscopy around λ = 3.1-3.4 µm.

Interaction of Venturicidin and F·F-ATPase/ATP Synthase of Tightly Coupled Subbacterial Particles of Paracoccus denitrificans in Energized Membranes.

Proton-translocating F×F-ATPase/synthase that catalyzes synthesis and hydrolysis of ATP is commonly considered to be a reversibly functioning complex. We have previously shown that venturicidin, a specific F-directed inhibitor, blocks the synthesis and hydrolysis of ATP with a significant difference in the affinity [Zharova, T. V.

Monolayer-Scale GaN/AlN Multiple Quantum Wells for High Power e-Beam Pumped UV-Emitters in the 240-270 nm Spectral Range.

Monolayer (ML)-scale GaN/AlN multiple quantum well (MQW) structures for electron-beam-pumped ultraviolet (UV) emitters are grown on -sapphire substrates by using plasma-assisted molecular beam epitaxy under controllable metal-rich conditions, which provides the spiral growth of densely packed atomically smooth hillocks without metal droplets. These structures have ML-stepped terrace-like surface topology in the entire QW thickness range from 0.75-7 ML and absence of stress at the well thickness below 2 ML.

Room-temperature Fe:ZnSe laser tunable in the spectral range of 3.7-5.3 µm applied for intracavity absorption spectroscopy of CO isotopes, CO and NO.

We demonstrate an intracavity absorption spectroscopy system based on a broadband single-crystal pulsed Fe:ZnSe laser. The laser operates at room-temperature and is continuously tunable in the spectral range of 3.76-5.

Lack of Excitation Energy Transfer from the Bacteriochlorophyll Soret Band to Carotenoids in Photosynthetic Complexes of Purple Bacteria.

The excitation energy transfer (EET) from the bacteriochlorophyll (BChl) Soret band to the second excited state(s) (S) of carotenoids in pigment-protein complexes of purple bacteria was investigated. The efficiency of EET was determined, based on fluorescence excitation and absorption spectra of chromatophores, peripheral light-harvesting complexes (LH2), core complexes (LH1-RC), and pigments in solution. Carotenoid-containing and carotenoid-less samples were compared: LH1-RC and LH2 from , , and chromatophores from and wild type and carotenoid-free strains R-26 and G9.

Tunable in the range of 4.5-6.8 µm room temperature single-crystal Fe:CdTe laser pumped by Fe:ZnSe laser.

We report a laser operation from a Fe:CdTe single crystal, pumped by 40-ns pulses of a 4.12-µm Fe:ZnSe laser. The maximum output energy of 5.

Unique features of the 'photo-energetics' of purple bacteria: a critical survey by the late Aleksandr Yuryevich Borisov (1930-2019).

We provide here an edited version of the "Farewell discussion" by the late Aleksandr (Alex) Yuryevich (Yu) Borisov (1930-2019) on several aspects related to the excitation energy transfer in photosynthetic bacteria. It is preceded by a prolog giving the events that led to our decision to publish it. Further, we include here a few photographs to give a personal glimpse of this unique biophysicist of our time.

High-efficiency continuous-wave single-mode room-temperature operation of Cr:CdSe single-crystal laser with output power of 2.3 W.

We report on the study of quenching and thermal lensing based on simple effective lens approximation in a Cr:CdSe active medium, including detailed research on the medium's luminescence lifetime dependence on temperature in the 236-391 K range. This work has allowed us to partially overcome the limitations associated with thermal effects in the medium and build a laser system that allowed power scalability to be realized for the Cr:CdSe laser. Longitudinal pumping using a continuous-wave Tm-doped fiber laser at 1.

High-efficiency high-repetition-rate gain-switched operation around 3 μm in Cr:CdSe single-crystal laser pumped by fiber-laser-pumped Ho:YAG laser.

We report the efficient gain-switched high-repetition-rate Cr:CdSe single-crystal laser operating around 3 μm and pumped at 2.09 μm by a fiber-laser-pumped Ho:YAG laser. Average power of up to 6 W with the optical-to-optical efficiency of 67% at 2.

Respiratory complex II: ROS production and the kinetics of ubiquinone reduction.

Bovine heart mitochondrial respiratory complex II generates ROS, mostly as superoxide, at the rate of about 20% of that detected during simultaneous operation of complex I and II when oxidation of ubiquinol is prevented by myxothiazol. ROS generating activity at different fumarate/succinate concentrations ratio implies that an enzyme component with a midpoint potential 40mV more positive than that of fumarate/succinate couple is the donor for one-electron reduction of oxygen. This suggests that the iron-sulfur cluster(s) is(are) involved in superoxide formation.

High-Output-Power Ultraviolet Light Source from Quasi-2D GaN Quantum Structure.

Quasi-2D GaN layers inserted in an AlGaN matrix are proposed as a novel active region to develop a high-output-power UV light source. Such a structure is successfully achieved by precise control in molecular beam epitaxy and shows an amazing output power of ≈160 mW at 285 nm with a pulsed electron-beam excitation. This device is promising and competitive in non-line-of-sight communications or the sterilization field.

Red chlorophyll excitation dynamics in Arthrospira platensis photosystem I trimeric complexes as studied by femtosecond transient absorption spectroscopy.

Femtosecond absorption spectroscopy was applied to study for the first time excitation dynamics in isolated photosystem I trimers from Arthrospira platensis, which display extremely long-wavelength absorption peaks. Pump-probe spectra observed at 77K in the timescale of dozens of picoseconds upon 70-fs excitation revealed two maxima near 710 and 730 nm, which correspond to red chlorophyll forms. Bleaching at 680 nm developed in ∼ 200 fs, whereas the bleaching kinetics at 710 and 730 nm exhibited two components with time constants of 1 and 5.