Ten-Nanosecond Step-Scan FT-IR Absorption Difference Time-Resolved Spectroscopy: Applications to Excited States of Transition Metal Complexes

1997 ◽  
Vol 51 (4) ◽  
pp. 580-583 ◽  
Author(s):  
Pingyun Chen ◽  
Richard A. Palmer
Keyword(s):  
Excited State ◽  
Excited States ◽  
Signal To Noise Ratio ◽  
Ir Absorption ◽  
Decay Kinetics ◽  
Time Resolved ◽  
Ligand Charge Transfer ◽  
Ft Ir ◽  
Good Signal ◽  
Nanosecond Time Resolution

Ten-nanosecond time resolution has been achieved with step-scan FT-IR absorbance difference spectroscopy (S2FT-IR Δ A TRS) and demonstrated by measuring Δ A spectra of fac-[Re(bpy)(CO)3Cl] and cis-[Os(bpy)2(CO)(4,4′-bpy)]2+ (bpy = 2,2′-bipyridine; 4,4′-bpy=4,4′-bipyridine) in CH3CN solution, following 355-nm laser excitation. In both complexes, the large shifts in (CO) to higher energy are consistent with the assignment that the lowest-energy excited states are metal-to-ligand charge transfer in nature. For [Os(bpy)2(CO)(4,4′-bpy)]2+, it is also possible to measure the excited-state decay kinetics, again with 10-ns resolution. In addition, Δ A bands are observed that are related to excited-state vibrations of the bipyridine ligands. Δ A spectra of good signal-to-noise ratio can be obtained for complexes with lifetimes as short as 10 ns.

Study of Impulse Polymer Rheo-Optics by Step-Scan FT-IR Time-Resolved Spectroscopy

1997 ◽  
Vol 51 (8) ◽  
pp. 1245-1250 ◽  
Author(s):  
Haochuan Wang ◽  
Richard A. Palmer ◽  
Christopher J. Manning
Keyword(s):  
Ir Spectroscopy ◽  
Frequency Domain ◽  
Time Domain ◽  
Optical Measurement ◽  
Signal To Noise Ratio ◽  
Molecular Reorientation ◽  
Time Resolved ◽  
Ft Ir ◽  
Good Signal ◽  
Ft Ir Spectroscopy

The applicability of step-scan impulse/response FT-IR spectroscopy to the rheo-optical study of polymer films is demonstrated by spectral measurements with isotactic polypropylene. A novel piezoelectrically driven microrheometer is employed to apply repetitive impulses to a polymer sample while time-domain spectra are recorded by step-scan FT-IR spectroscopy. The traditional advantages of Fourier transform spectroscopy are retained while providing a second multiplex advantage for the characterization of the time-dependence of the sample response. Reproducible results, consistent with the frequency-domain literature data and having good signal-to-noise ratio, are obtained. The spectral changes due to molecular reorientation are found to be essentially as fast as the mechanical stretching, also consistent with frequency-domain results. To our knowledge, this is the first reported step-scan FT-IR time-domain rheo-optical measurement. This technique appears to be applicable to a variety of polymer samples. The advantages of time-domain measurements over frequency-domain measurements are briefly discussed.

scholarly journals Ground- and excited-state characteristics in photovoltaic polymer N2200

RSC Advances ◽  
2021 ◽  
Author(s):  
Guanzhao Wen ◽  
Xianshao Zou ◽  
Rong Hu ◽  
Jun Peng ◽  
Zhifeng Chen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Excited State ◽  
Steady State ◽  
Excited States ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Time Dependent ◽  
Functional Theory ◽  
Time Resolved ◽  
Dependent Density

Ground- and excited-states properties of N2200 have been studied by steady-state and time-resolved spectroscopies as well as time-dependent density functional theory calculations.

Time-Resolved FT-IR Absorption Spectroscopy Using a Step-Scan Interferometer

1991 ◽  
Vol 45 (3) ◽  
pp. 390-397 ◽  
Author(s):  
Wolfgang Uhmann ◽  
Andreas Becker ◽  
Christoph Taran ◽  
Friedrich Siebert
Keyword(s):  
Absorption Spectroscopy ◽  
Ir Absorption ◽  
Time Resolved ◽  
Ft Ir

scholarly journals First steps towards time-resolved 'in-house' X-ray diffraction experiments

2014 ◽  
Vol 70 (a1) ◽  
pp. C775-C775 ◽  
Author(s):  
Radoslaw Kaminski ◽  
Jason Benedict ◽  
Elzbieta Trzop ◽  
Katarzyna Jarzembska ◽  
Bertrand Fournier ◽  
...  
Keyword(s):  
Excited State ◽  
Time Resolution ◽  
Structural Changes ◽  
Laser Pulses ◽  
High Repetition Rate ◽  
X Ray Diffraction ◽  
Laboratory Equipment ◽  
Time Resolved ◽  
X Ray ◽  
Ligand Charge Transfer

High-intensity X-ray sources, such as synchrotrons or X-ray free electron lasers, providing up to 100 ps time-resolution allow for studying very short-lived excited electronic states in molecular crystals. Some recent examples constitute investigations of Rh...Rh bond shortening,[1] or metal-to-ligand charge transfer processes in CuI complexes.[2] Nevertheless, in cases in which the lifetime of excited state species exceeds 10 μs it is now possible, due to the dramatic increase in the brightness of X-ray sources and the sensitivity of detectors, to use laboratory equipment to explore structural changes upon excitation. Consequently, in this contribution we present detailed technical description of the 'in-house' X-ray diffraction setup allowing for the laser-pump X-ray-probe experiments within the time-resolution at the order of 10 μs or larger. The experimental setup consists of a modified Bruker Mo-rotating-anode diffractometer, coupled with the high-frequency Nd:YAG laser (λ = 355 nm). The required synchronization of the laser pulses and the X-ray beam is realized via the optical chopper mounted across the beam-path. Chopper and laser capabilities enable high-repetition-rate experiments reaching up to 100 kHz. In addition, the laser shutter is being directly controlled though the original diffractometer software, allowing for collection of the data in a similar manner as done at the synchrotron (alternating light-ON & light-OFF frames). The laser beam itself is split into two allowing for improved uniform light delivery onto the crystal specimen. The designed setup was tested on the chosen set of crystals exhibiting rather long-lived excited state, such as, the Cu2Br2L2 (L = C5H4N-NMe2) complex, for which the determined lifetime is about 100 μs at 90 K. The results shall be presented. Research is funded by the National Science Foundation (CHE1213223). KNJ is supported by the Polish Ministry of Science and Higher Education through the "Mobility Plus" program.

scholarly journals Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands

Inorganics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 14
Author(s):  
Patrick Herr ◽  
Oliver S. Wenger
Keyword(s):  
Excited State ◽  
Excited States ◽  
Quantum Yields ◽  
Nonradiative Relaxation ◽  
Temperature Dependent ◽  
Tert Butyl ◽  
Thermally Activated ◽  
Ligand Charge Transfer ◽  
Order Of Magnitude ◽  
Electronic Ground

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic RuII polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo0 complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to RuII polypyridines, the molecular distortions in the luminescent 3MLCT state relative to the electronic ground state seem to be smaller in the Mo0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo0 tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)3]2+.

A density functional theory and spectroscopic study of intramolecular quenching of metal-to-ligand charge-transfer excited states in some mono-bipyridine ruthenium(II) complexes

2014 ◽  
Vol 92 (10) ◽  
pp. 996-1009 ◽  
Author(s):  
Shivnath Mazumder ◽  
Ryan A. Thomas ◽  
Richard L. Lord ◽  
H. Bernhard Schlegel ◽  
John F. Endicott
Keyword(s):  
Density Functional Theory ◽  
Excited State ◽  
Charge Transfer ◽  
Excited States ◽  
Lower Energy ◽  
Density Functional ◽  
Dimethyl Sulfide ◽  
Intramolecular Electron Transfer ◽  
Functional Theory ◽  
Ligand Charge Transfer

The complexes [Ru(NCCH3)4bpy]2+ and [Ru([14]aneS4)bpy]2+ ([14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane, bpy = 2,2′-bipyridine) have similar absorption and emission spectra but the 77 K metal-to-ligand charge-transfer (MLCT) excited state emission lifetime of the latter is less than 0.3% that of the former. Density functional theory modeling of the lowest energy triplet excited states indicates that triplet metal centered (3MC) excited states are about 3500 cm−1 lower in energy than their 3MLCT excited states in both complexes. The differences in excited state lifetimes arise from a much larger coordination sphere distortion for [Ru(NCCH3)4bpy]2+ and the associated larger reorganizational barrier for intramolecular electron transfer. The smaller ruthenium ligand distortions of the [Ru([14]aneS4)bpy]2+ complex are apparently a consequence of stereochemical constraints imposed by the macrocyclic [14]aneS4 ligand, and the 3MC excited state calculated for the unconstrained [Ru(S(CH3)2)4bpy]2+ complex (S(CH3)2 = dimethyl sulfide) is distorted in a manner similar to that of [Ru(NCCH3)4bpy]2+. Despite the lower energy calculated for its 3MC than 3MLCT excited state, [Ru(NCCH3)4bpy]2+ emits strongly in 77 K glasses with an emission quantum yield of 0.47. The emission is biphasic with about a 1 μs lifetime for its dominant (86%) emission component. The 405 nm excitation used in these studies results in a significant amount of photodecomposition in the 77 K glasses. This is a temperature-dependent biphotonic process that most likely involves the bipyridine-radical anionic moiety of the 3MLCT excited state. A smaller than expected value found for the radiative rate constant is consistent with a lower energy 3MC than 3MLCT state.

Time-resolved XAFS measurement using quick-scanning techniques at BSRF

2017 ◽  
Vol 24 (3) ◽  
pp. 674-678 ◽  
Author(s):  
Shengqi Chu ◽  
Lirong Zheng ◽  
Pengfei An ◽  
Hui Gong ◽  
Tiandou Hu ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
High Energy ◽  
High Energy Resolution ◽  
Double Crystal ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
Double Crystal Monochromator ◽  
Good Signal ◽  
X Ray Absorption

A new quick-scanning X-ray absorption fine-structure (QXAFS) system has been established on beamline 1W1B at the Beijing Synchrotron Radiation Facility. As an independent device, the QXAFS system can be employed by other beamlines equipped with a double-crystal monochromator to carry out quick energy scans and data acquisition. Both continuous-scan and trapezoidal-scan modes are available in this system to satisfy the time scale from subsecond (in the X-ray absorption near-edge structure region) to 1 min. Here, the trapezoidal-scan method is presented as being complementary to the continuous-scan method, in order to maintain high energy resolution and good signal-to-noise ratio. The system is demonstrated to be very reliable and has been combined with in situ cells to carry out time-resolved XAFS studies.

Characterization of Rhodamine 6G-Doped Thin Sol-Gel Films

1993 ◽  
Vol 47 (2) ◽  
pp. 229-234 ◽  
Author(s):  
Upvan Narang ◽  
Frank V. Bright ◽  
Paras N. Prasad
Keyword(s):  
Excited State ◽  
Rhodamine 6G ◽  
Sol Gel ◽  
Decay Kinetics ◽  
Time Resolved ◽  
Laser Illumination ◽  
State Decay ◽  
Sol Gel Films ◽  
Microscope Slides

Rhodamine 6G- (R6G) doped thin sol-gel films were cast on glass microscope slides and characterized with the use of steady-state and time-resolved fluorescence spectroscopy. The fluorescence intensity, photodegradation under laser illumination, and excited-state decay kinetics were all investigated as a function of dopant concentration. The excited-state decay kinetics of highly doped films show clear evidence of R6G aggregation. Photodegradation under laser illumination is very interesting and is discussed in detail.

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