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Multi-mode heterodyned 5th-order infrared spectroscopy
摘要： Fifth-order multidimensional infrared spectroscopy with heterodyned detection was carried out in the three-beam dual-frequency configuration. Numerous 5th-order cross peaks were detected for the 4-azidobutyrate-N-hydroxysuccinimide ester compound in solution involving several vibrational modes ranging in frequency from 1045 to 2100 cm?1. Cross peaks involving overtones (2X/Z) and combination bands (XY/Z) among the tags, modes X and Y excited by the first two mid-IR laser pulses, and the reporter, modes Z excited by the third laser pulse, were acquired and the factors affecting the amplitude of 5th-order cross peaks are discussed. The 5th-order cross peaks were detected among modes that are spatially close (a few bonds apart) as well as for modes spatially separated by ca. 12 ? (eight bonds apart). In both cases, the waiting time dependences for the 3rd and 5th order cross peaks were found to be different. In particular, the waiting time at which the cross-peak maximum is reached, the decay time, and the value of a plateau at large waiting times were all differing strongly. The differences are explained by reduced sensitivity of the 5th-order signals to modes coupled weakly to the reporter mode and different relaxation dynamics involving overtone state of the tag. The ability of the 5th-order peaks to single out the modes coupled strongly to the reporter can help identifying specific energy relaxation and transport pathways, which will be useful for understanding energy transport dynamics in molecules. The absorptive 5th-order cross peaks were constructed which report on three-point correlation functions. It is shown that in addition to the triple-frequency correlation functions, a correlation of the frequencies with the mode coupling (anharmonicity) can be naturally measured by the 5th-order spectroscopy. The current limit for detecting 5th-order signals was estimated at the level of 1 × 10?3 in reduced anharmonicity, which is determined by the corresponding two-state anharmonicity divided by the reporter mode spectral width. Given the simplicity of recording the 5th-order cross peaks in the three-beam configuration, the approach carries a potential for a broad use.
关键词： vibrational modes,anharmonicity,heterodyned detection,fifth-order,multidimensional infrared spectroscopy,energy transport
更新于2025-09-23 15:22:29
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Time-Resolved Impulsive Stimulated Raman Spectroscopy with Synchronized Triple Mode-Locked Lasers
摘要： A complete understanding of a photochemical reaction dynamics begins with real-time measurements of both electronic and vibrational structures of photoexcited molecules. Time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS) with femtosecond actinic pump, Raman pump, and Raman probe pulses is one of the incisive techniques enabling one to investigate the structural changes of photoexcited molecules. Here, we demonstrate that such femtosecond TR-ISRS is feasible with synchronized triple mode-locked lasers without using any time-delay devices. Taking advantage of precise control of the three repetition rates independently, we could achieve automatic scanning of two delay times between the three pulses, which makes both rapid data acquisition and wide dynamic range measurement of the fifth-order TR-ISRS signal achievable. We thus anticipate that the present triple mode-locked laser-based TR-ISRS technique will be of critical use for long-term monitoring of photochemical reaction dynamics in condensed phases and biological systems.
关键词： pump-dump-probe,fifth-order electronic spectroscopy,impulsive stimulated Raman spectroscopy,femtosecond Raman scattering,Time-resolved vibrational spectroscopy
更新于2025-09-23 15:21:01
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Influence of the Fifth-Order Nonlinearity of Gold Nanorods on the Performance of Random Lasers
摘要： We present the first experimental evidence for the influence of the fifth-order nonlinearity on the characteristics of Random Lasers with plasmonic nanoparticles as scatterers. The experiments were performed with gold nanorods suspended in an ethanolic solution of Rhodamine 6G, pumped by a picosecond laser. It is shown that by varying the nanorods aspect-ratio, it is possible to control the cooperative influence of both transverse and longitudinal localized surface plasmons on the fifth-order nonlinear light scattering, a phenomenon that allows to manage the optical feedback causing significant changes in the threshold intensity and emission power of Random Lasers.
关键词： fifth-order nonlinearity,gold nanorods,Random Lasers,optical feedback,plasmonic nanoparticles
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE Industry Applications Society Annual Meeting - Baltimore, MD, USA (2019.9.29-2019.10.3)] 2019 IEEE Industry Applications Society Annual Meeting - Control of Single Phase Solar Photovoltaic Supply System
摘要： This work deals with the modified multilayer fifth order generalized integrator (MLFOGI) based grid tied single phase solar photovoltaic (PV) system employing fuzzy logic control (FLC) based maximum power point tracking (MPPT) algorithms. The MLFOGI is used to extract the fundamental component of grid voltage under polluted grid due to voltage sag, swell, harmonics, frequency variations and dc offsets. The FLC based MPPT is capable to extract optimum energy under change in weather conditions. It offers fast dynamic response under reduced PV voltage oscillation. The proposed system is developed on MATLAB 2018a and obtained results shows the feasibility of system control and Total Harmonics Distortions (THDs) of grid current are in acceptable limits as per IEEE-519 standard.
关键词： Multilayer Fifth Order Generalized Integrator (MLFOGI),Maximum Power Point Tracing (MPPT),Fuzzy Logic Control (FLC),Voltage Source Inverter (VSI),Solar Photovoltaic System (SPV)
更新于2025-09-11 14:15:04