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Photo-physical properties of substituted 2,3-distyryl indoles: Spectroscopic, computational and biological insights
摘要： The structural dependence of the photo-physical properties of substituted 2,3-distyryl (23DSI) indoles were studied using several spectroscopic techniques including steady-state UV-VIS spectroscopy, steady-state fluorescence spectroscopy, steady-state excitation spectroscopy, time correlated single photon counting (TCSPC) spectroscopy, and time-resolved fluorescence upconversion spectroscopy (TRFLS). Each of 23DSI derivatives investigated showed distinct fluorescence emission and UV-VIS spectra, indicating strong structural dependence of the emission and the excitation. The UV-VIS spectra of the 23DSI derivatives showed three main identical absorption bands with minor deviations in the absorbance caused by substituent groups on the distyryl rings. The time-resolved fluorescence up-conversion studies indicated that the fluorescence undergoes a mono-exponential decay whereas the calculated fluorescence lifetime showed relatively short fluorescence lifetimes of approximately 1 ns. All of the 23DSI derivatives showed two-photon absorption upon direct excitation of 1.6 W laser pulses at 800 nm. These studies suggest that the substituents, attached to distyryl core, are capable of boosting or hindering fluorescence intensities by distorting the π-conjugation of the 23DSI molecule. Our studies showed that 23DSI (p-F) has the highest fluorescence emission quantum yield. Theoretical calculations for the ground state of 23DSI derivatives confirmed differences in electron densities in 23DSI derivatives in the presence of different substituent attachments. The excellent fluorescence emission, high fluorescence quantum yield and two-photon absorption properties of these 23DSI molecules make them attractive candidates for potential applications in the fields of biological imaging, biomedicine, fluorescent probes, and photodynamic inactivation (PDI). B. subtilis samples, treated with micro molar solutions of 23DSI (p-OCH3) and 23DSI (p-CH3), showed very effective photodynamic inactivation (PDI) upon irradiation with white light.
关键词： Two photon absorption,Time-resolved fluorescence upconversion laser spectroscopy,Photodynamic inactivation,Gaussian calculations,Photo-physical properties,Light-activation
更新于2025-11-14 15:26:12
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Realization of a infrared detector free of bandwidth limit based on quartz crystal tuning fork
摘要： A new type of photoelectric detector based on a standard quartz crystal tuning fork (QCTF) with resonant frequency of ～32 kHz is developed for infrared spectroscopy applications. Analogous to the photoelectric effect of traditional semiconductor detectors, we utilize the piezoelectric effect of the QCTF to gauge the light intensity. To demonstrate this technique, the spectral absorption features of C2H2 molecule have been recorded and compared with a commercial mercury cadmium-telluride (MCT) detector. The proposed detection technique may pave a new way towards developing a new type of photodetector without bandwidth limit and complicated cryogenic cooling.
关键词： Infrared detector,Piezoelectric effect,QCTF,Laser spectroscopy
更新于2025-09-23 15:23:52
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High-precision collinear laser spectroscopy at the Collinear Apparatus for Laser Spectroscopy and Applied Physics (COALA)
摘要： COALA is a new offline collinear laser spectroscopy setup for high-precision measurements and development work at TU Darmstadt, Germany. An introduction to the technique and the experimental setup is given and an overview of current projects with recent results is presented. The idea of a novel all-optical absolute charge radius determination is discussed.
关键词： Nuclear charge radii,High voltage evaluation,High precision spectroscopy,Collinear laser spectroscopy
更新于2025-09-23 15:21:01
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Mechanism of the Laser Flash Photolysis of Rydimeric e-Tautomers of 4-N,N-Diethylaminoazobenzene in a 2-Propanol Medium
摘要： Difference transit absorption spectra (TASes) obtained via flash photolysis of isopropanol solutions of 4-N,N-diethylaminoazobenzene (DEAB) using 15 ns laser pulses at wavelengths of λex = 265 and 353 nm are analyzed. The inconsistency of constructing the mechanism of trans (t) → cis (c) photisomerization of DEAB based on the concept of this dye having a monomeric structure is shown. Based on the rydimeric concept of aminoazobenzene dyes, which include Rydberg dimers DEAB2, an adequate explanation is given of the nature of TAS signals with structures that change dramatically when in wavelength λex is altered. TAS signals of DEAB2 are compared to ultrahigh-speed (subpico- and pico-second) TAS signals of rydimers of a reference aminoazobenzene (AAB2) dye. It is established that the main difference between the structures of DEAB2 TAS signals generated by pulses with indicated wavelengths λex is due to the excitation of various rydimeric e-tautomers. In addition, a rydimeric e-tautomer that is unstable in the ground state acquires increased stability in propanol and, by absorbing radiation with λex = 353 nm, alters the structure of one of its monomers to quinoid while remaining a rydimer. It is shown that when excited with radiation pulses at λex = 265 nm, a rydimeric e-tautomer (which is more stable in the ground state) dissociates into individual monomers, one of which isomerizes to form cis-DEAB molecules.
关键词： diethylaminoazobenzene rydimers,rydimer photonics,laser flash photolysis,trans–cis isomerization,visible laser spectroscopy
更新于2025-09-23 15:21:01
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On the performance of wavelength meters: Part 1a??consequences for medium-to-high-resolution laser spectroscopy
摘要： Present-day laser-spectroscopy experiments increasingly rely on modern commercial devices to monitor, stabilize, and scan the wavelength of their probe laser. Recently, new techniques are capable of achieving unprecedented levels of precision on atomic and nuclear observables, pushing these devices to their performance limits. Considering the fact that these observables themselves are deduced from the frequency difference between specific atomic resonances, in the order of MHz–GHz, the uncertainty on the output of the device measuring the wavelength is often directly related to the final systematic uncertainty on the experimental results. Owing to its importance, the performance of several commercial wavelength meters was compared against different reference sources, including a Scanning Fabry–Pérot Interferometer (SFPI) and a frequency comb. Reproducible, wavelength- and device-dependent disagreements are observed, potentially skewing the experimental output at high precision. In this paper, a practical and relatively inexpensive wavelength meter characterization procedure is presented and validated. This method is capable of improving the precision on wavelength differences considerably depending on the device, while together with a second investigation that is published separately, (K?nig et al., in Appl Phys B, 2020), it offers a full description of the expected wavelength meter performance for users.
关键词： frequency comb,hyperfine structure,laser spectroscopy,wavelength meters,Scanning Fabry–Pérot Interferometer
更新于2025-09-23 15:21:01
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Laser spectroscopy of pionic helium atoms
摘要： Charged pions are the lightest and longest-lived mesons. Mesonic atoms are formed when an orbital electron in an atom is replaced by a negatively charged meson. Laser spectroscopy of these atoms should permit the mass and other properties of the meson to be determined with high precision and could place upper limits on exotic forces involving mesons (as has been done in other experiments on antiprotons). Determining the mass of the π? meson in particular could help to place direct experimental constraints on the mass of the muon antineutrino. However, laser excitations of mesonic atoms have not been previously achieved because of the small number of atoms that can be synthesized and their typically short (less than one picosecond) lifetimes against absorption of the mesons into the nuclei. Metastable pionic helium (π4He+) is a hypothetical three-body atom composed of a helium-4 nucleus, an electron and a π? occupying a Rydberg state of large principal (n ≈ 16) and orbital angular momentum (l ≈ n ? 1) quantum numbers. The π4He+ atom is predicted to have an anomalously long nanosecond-scale lifetime, which could allow laser spectroscopy to be carried out. Its atomic structure is unique owing to the absence of hyperfine interactions between the spin-0 π? and the 4He nucleus. Here we synthesize π4He+ in a superfluid-helium target and excite the transition (n, l) = (17, 16) → (17, 15) of the π?-occupied π4He+ orbital at a near-infrared resonance frequency of 183,760 gigahertz. The laser initiates electromagnetic cascade processes that end with the nucleus absorbing the π? and undergoing fission. The detection of emerging neutron, proton and deuteron fragments signals the laser-induced resonance in the atom, thereby confirming the presence of π4He+. This work enables the use of the experimental techniques of quantum optics to study a meson.
关键词： pionic helium atoms,Laser spectroscopy,mesons,quantum optics
更新于2025-09-23 15:21:01
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Frequency comb interference spectroscopy using a fiber laser comb and a multi-colour laser
摘要： In this paper, we demonstrate a rapid high-resolution frequency comb spectrometer involving a mode-locked laser comb and a multi-colour laser. The heterodyne detection of the two lasers enables hundreds of thousands of Doppler-limited molecular spectra to be recorded in a second. With this device, several P-branch transitions of the H13CN (gas) 2ν3-band are simultaneously interrogated at comb-line-defined resolution (54.5 MHz or 0.5 pm) within 3 μs. The single-measurement spectrum spans >200 GHz (~1.6 nm) far beyond the electronic bandwidth (33 GHz) of our acquisition system. Without using asynchronous combs or dispersers and detection arrays, the spectrometer may benefit many gas sensing applications, such as environmental monitoring.
关键词： frequency comb,fiber laser,spectroscopy
更新于2025-09-23 15:21:01
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Filament studies for laser spectroscopy on lawrencium
摘要： The sensitive RAdiation Detected Resonance Ionization Spectroscopy (RADRIS) technique enabled the study of the atomic structure of the element nobelium (No, Z =102) for the first time. The prospect of accessing the next element, lawrencium (Lr, Z =103), depends on the efficiency and speed of evaporation of sample atoms from a filament catcher. To determine the desorption properties with respect to the requirements for the RADRIS technique, an off-line set-up to characterize filament catchers was developed. Using the iso-electronic homologue lutetium (Lu, Z=71) different filament materials were studied with respect to the required desorption temperatures and the background from surface ionization.
关键词： Lawrencium,Laser spectroscopy
更新于2025-09-23 15:21:01
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Highly selective two-step laser ionization schemes for the analysis of actinide mixtures
摘要： Resonance ionization mass spectroscopy has proven to be a very efficient and selective method for the spatially resolved ultratrace determination of actinide contaminations, and the analysis of specific element and isotopic distributions on surfaces and environment particles. We report on the identification of highly element-selective optical excitation schemes identified for this purpose, with a particular focus on the precise determination of the isobaric ratios of 235U to 239Pu as well as 243Am to 241Pu. The chosen two-step ionization schemes were characterized with respect to their element selectivity on synthetic multi-element actinide mixtures, with an element ratio Pu : Am : U of 1 : 10 : 104, a composition which is typical, e.g., for spent nuclear reactor fuels.
关键词： Mass spectrometry,Actinides,Laser spectroscopy,Multi-element mixture,Isotope ratio
更新于2025-09-23 15:21:01
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Collinear laser spectroscopy of stable palladium isotopes at the IGISOL facility
摘要： Collinear laser spectroscopy on stable palladium isotopes was performed at the IGISOL facility in Jyv¨askyl¨a in preparation for an experiment on its neutron-rich isotopes. Five transitions from different initial atomic states were tested, with the goal of finding the most spectroscopically efficient. The observed intensities afforded a comparison with atomic-level population predictions based on charge-exchange calculations. For some transitions hyperfine parameters of 105Pd were measured, which were found to be in good agreement with literature values. A King plot analysis was performed using the measured isotope shifts and known charge radii from literature to determine the atomic field and mass shift factors.
关键词： Palladium,Collinear laser spectroscopy,IGISOL
更新于2025-09-23 15:21:01