scholarly journals Ultrafast dephasing in hydrogen-bonded pyridine–water mixtures

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 234-240
Author(s):  
Gombojav O. Ariunbold ◽  
Bryan Semon ◽  
Supriya Nagpal ◽  
Yuri Rostovtsev
Keyword(s):  
Spectroscopic Technique ◽  
Pulse Excitation ◽  
Water Molecules ◽  
Raman Spectroscopic ◽  
Time Frequency ◽  
Spectral Peaks ◽  
Coherent Raman ◽  
Anti Stokes ◽  
Triangular Ring ◽  
Hydrogen Bonded

Abstract Hydrogen-bonded mixtures with varying concentration are a complicated networked system that demands a detection technique with both time and frequency resolutions. Hydrogen-bonded pyridine–water mixtures are studied by a time-frequency resolved coherent Raman spectroscopic technique. Femtosecond broadband dual-pulse excitation and delayed picosecond probing provide sub-picosecond time resolution in the mixtures temporal evolution. For different pyridine concentrations in water, asymmetric blue versus red shifts (relative to pure pyridine spectral peaks) were observed by simultaneously recording both the coherent anti-Stokes and Stokes Raman spectra. Macroscopic coherence dephasing times for the perturbed pyridine ring modes were observed in ranges of 0.9–2.6 ps for both 18 and 10 cm − 1 10\hspace{0.33em}{{\rm{cm}}}^{-1} broad probe pulses. For high pyridine concentrations in water, an additional spectral broadening (or escalated dephasing) for a triangular ring vibrational mode was observed. This can be understood as a result of ultrafast collective emissions from coherently excited ensemble of pairs of pyridine molecules bound to water molecules.

Coherent Anti-Stokes–Stokes Raman Cross-Correlation Spectroscopy: Asymmetric Frequency Shifts in Hydrogen-Bonded Pyridine-Water Complexes

2019 ◽  
Vol 73 (9) ◽  
pp. 1099-1106 ◽  
Author(s):  
Gombojav O. Ariunbold ◽  
Bryan Semon ◽  
Supriya Nagpal ◽  
Prakash Adhikari
Keyword(s):  
Hydrogen Bonding ◽  
Raman Spectra ◽  
Probe Pulse ◽  
Deep Understanding ◽  
Spectroscopic Technique ◽  
Correlation Spectroscopy ◽  
Label Free ◽  
Coherent Raman ◽  
Anti Stokes ◽  
Hydrogen Bonded

Hydrogen bonding is a vital molecular interaction for bio-molecular systems, yet deep understanding of its ways of creating various complexes requires extensive empirical testing. A hybrid femtosecond/picosecond coherent Raman spectroscopic technique is applied to study pyridine-water complexes. Both the coherent Stokes and anti-Stokes Raman spectra are recorded simultaneously as the concentration of water in pyridine varied. A 3 ps and 10 cm−1 narrowband probe pulse enables us to observe well-resolved Raman spectra. The hydrogen bonding between pyridine and water forms the complexes that have altered vibrational frequencies. These red and blue shifts were observed to be uneven. This asymmetry was result of the generated background nonlinear optical processes of pyridine-water complexes. This asymmetry tends to disappear as probe pulse further delayed attaining background-free coherent Raman spectra. For better visualization, spectral analyses both traditional two-dimensional correlation spectroscopy and recent second-order correlation functions defined in frequency domain are employed. Recognized as a label-free and background-free technique, the coherent Raman spectroscopy, complemented with a known high-resolution spectroscopic correlation analysis, has potential in studying the hydrogen-bonded pyridine-water complexes. These complexes are of great biological importance both due to the ubiquitous nature of hydrogen bonds and due to the close resemblance to chemical bases in macro-biomolecules.

scholarly journals Coherent anti-Stokes Raman spectroscopy: Understanding the essentials

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Gombojav O. Ariunbold ◽  
Narangerel Altangerel
Keyword(s):  
Raman Spectroscopy ◽  
Raman Scattering ◽  
Raman Spectra ◽  
Error Function ◽  
Ultrashort Pulses ◽  
Spectroscopic Technique ◽  
Background Suppression ◽  
Closed Form Solutions ◽  
Coherent Raman ◽  
Anti Stokes

AbstractThis paper is a brief overview to coherent anti- Stokes Raman spectroscopic technique and introduces the strengths and barriers to its use all based on the interpretation of simple theoretical formulae. The use of the Gaussian ultrashort pulses is highlighted as a practical elucidatory reconstruction tool of coherent Raman spectra. The paper presents the integral formulae for coherent anti-Stokes and Stokes Raman scattering, and discusses the closed-form solutions, its complex error function, and the delay time formula for enhancement of the inferred pure coherent Raman spectra. As an example, the timeresolved coherent Stokes Raman scattering experimental observations are quantitatively elucidated.Understanding the essentials of coherent Raman spectroscopy, therefore, promotes the importance of a number of experiments including the ones utilizing a broadband excitation with a narrowband delayed probing for successful background suppression.

072 Sleep Spindle Harmonics in Insomnia

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A29-A30
Author(s):  
Michael Goldstein ◽  
Monika Haack ◽  
Janet Mullington
Keyword(s):  
Spectral Power ◽  
Nrem Sleep ◽  
Sleep Time ◽  
Sleep Spindle ◽  
Time Frequency ◽  
Insomnia Disorder ◽  
Spectral Peaks ◽  
Limited Application ◽  
Thalamic Relay Nuclei ◽  
Restorative Sleep

Abstract Introduction Prior research has reported NREM spectral EEG differences between individuals with insomnia and good-sleeper controls, including elevated high-frequency EEG power (beta/gamma bands, ~16-50Hz) and, to a lesser extent, elevations in sleep spindle parameters. However, the mechanisms driving these differences remain unclear. Harmonics have been observed in EEG data as spectral peaks at multiples of a fundamental frequency associated with an event (e.g., for a 14Hz spindle, the 2nd harmonic is expected to be a peak at 28Hz). Thus far, there has been very limited application of this idea of spectral harmonics to sleep spindles, even though these patterns can indeed be seen in some existing literature. We sought to build on this literature to apply spectral harmonic analysis to better understand differences between insomnia and good sleepers. Methods 15 individuals with insomnia disorder (DSM-5 criteria, 13 female, age 18–32 years) and 15 good-sleeper controls (matched for sex, age, and BMI) completed an overnight polysomnography recording in the laboratory and subsequent daytime testing. Insomnia diagnosis was determined by a board-certified sleep specialist, and exclusion criteria included psychiatric history within past 6 months, other sleep disorders, significant medical conditions, and medications with significant effects on inflammation, autonomic function, or other psychotropic effects. Results Consistent with prior studies, we found elevated sleep spindle density and fast sigma power (14-16Hz). Despite no difference in beta or gamma band power when averaged across NREM sleep, time-frequency analysis centered on the peaks of detected spindles revealed a phasic elevation in spectral power surrounding the 28Hz harmonic peak in the insomnia group, especially for spindles coupled with slow waves. We also observed an overall pattern of time-locked delay in the 28Hz harmonic peak, occurring approximately 40 msec after spindle peaks. Furthermore, we observed a 42Hz ‘3rd harmonic’ peak, not yet predicted by the existing modeling work, which was also elevated for insomnia. Conclusion In conjunction with existing mathematical modeling work that has linked sleep spindle harmonic peaks with thalamic relay nuclei as the primary generators of this EEG signature, these findings may enable novel insights into specific thalamocortical mechanisms of insomnia and non-restorative sleep. Support (if any) NIH 5T32HL007901-22

scholarly journals Cyclooctanaminium hydrogen succinate monohydrate

2012 ◽  
Vol 68 (4) ◽  
pp. o1204-o1204 ◽  
Author(s):  
Sanaz Khorasani ◽  
Manuel A. Fernandes
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Ammonium Cation ◽  
Water Molecules ◽  
Hydrated Salt ◽  
A Chain ◽  
Hydrogen Bonded

In the title hydrated salt, C8H18N+·C4H5O4−·H2O, the cyclooctyl ring of the cation is disordered over two positions in a 0.833 (3):0.167 (3) ratio. The structure contains various O—H.·O and N—H...O interactions, forming a hydrogen-bonded layer of molecules perpendicular to thecaxis. In each layer, the ammonium cation hydrogen bonds to two hydrogen succinate anions and one water molecule. Each hydrogen succinate anion hydrogen bonds to neighbouring anions, forming a chain of molecules along thebaxis. In addition, each hydrogen succinate anion hydrogen bonds to two water molecules and the ammonium cation.

Microplasma synthesized gold nanoparticles for surface enhanced Raman spectroscopic detection of methylene blue

2021 ◽  
Author(s):  
Xuanhe Li ◽  
Liangliang Lin ◽  
Wei-Hung Chiang ◽  
Kuan Chang ◽  
Hujun Xu
Keyword(s):  
Rapid Detection ◽  
Chemical Species ◽  
Spectroscopic Technique ◽  
Trace Level ◽  
Raman Spectroscopic ◽  
Non Invasive ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Non Destructive

Surface enhanced Raman scattering (SERS) is a powerful and sensitive spectroscopic technique that allows for rapid detection of trace-level chemical species in a non-invasive and non-destructive manner. In the present...

Syntheses and crystal structures of two magnesium–tetrazole compounds in salt and polymeric forms

2015 ◽  
Vol 71 (3) ◽  
pp. 222-228 ◽  
Author(s):  
Mohamed Abdellatif Bensegueni ◽  
Aouatef Cherouana ◽  
Slimane Dahaoui
Keyword(s):  
Alkaline Earth ◽  
Three Dimensional ◽  
Polymer Chains ◽  
Magnesium Ion ◽  
Water Molecules ◽  
Compound I ◽  
Hydrothermal Conditions ◽  
One Dimensional ◽  
Polymeric Chains ◽  
Hydrogen Bonded

Two alkaline earth–tetrazole compounds, namelycatena-poly[[[triaquamagnesium(II)]-μ-5,5′-(azanediyl)ditetrazolato-κ3N1,N1′:N5] hemi{bis[μ-5,5′-(azanediyl)ditetrazolato-κ3N1,N1′:N2]bis[triaquamagnesium(II)]} monohydrate], {[Mg(C2HN9)(H2O)3][Mg2(C2HN9)2(H2O)6]0.5·H2O}n, (I), and bis[5-(pyrazin-2-yl)tetrazolate] hexaaquamagnesium(II), (C5H3N6)[Mg(H2O)6], (II), have been prepared under hydrothermal conditions. Compound (I) is a mixed dimer–polymer based on magnesium ion centres and can be regarded as the first example of a magnesium–tetrazolate polymer in the crystalline form. The structure shows a complex three-dimensional hydrogen-bonded network that involves magnesium–tetrazolate dimers, solvent water molecules and one-dimensional magnesium–tetrazolate polymeric chains. The intrinsic cohesion in the polymer chains is ensured by N—H...N hydrogen bonds, which formR22(7) rings, thus reinforcing the propagation of the polymer chain along theaaxis. The crystal structure of magnesium tetrazole salt (II) reveals a mixed ribbon of hydrogen-bonded rings, of typesR22(7),R22(9) andR24(10), running along thecaxis, which are linked byR24(16) rings, generating a 4,8-cflunet.

scholarly journals Natural scientific methods in exploration of reference monuments of the Saka Culture in Kazakh Altai

2020 ◽  
pp. 21-31
Author(s):  
Zainolla Samashev ◽  
Aidos Erbulatovich Chotbaev ◽  
Nikolai Sergeevich Kurganov ◽  
Dmitrii Vasil'evich Pankin ◽  
Anastasiya Valer'evna Povolotskaya ◽  
...  
Keyword(s):  
Spectroscopic Technique ◽  
Organic Substances ◽  
Identification Procedure ◽  
Scientific Methods ◽  
Raman Spectroscopic ◽  
Gold Jewelry ◽  
Material Component ◽  
Modern Natural ◽  
East Kazakhstan ◽  
Subsequent Identification

This article explores the ancient gold jewelry with inlay, which were discovered in the process of archeological studies conducted in Summer 2018 of grave complexes located on the Eleke Sazy Plateau, Tarbagatay Ridge in East Kazakhstan Region in the burial of a young man belonging to aristocratic ancestry. It refers to the Saka culture, and dates back to approximately VIII-VII centuries BC. Among the discovered objects were garments embroidered with gold, quiver with arrows, and a bronze dagger in gold scabbard. This work studied the golden scabbard for dagger. The scabbard consists of several parts attached to a wooden base and decorated with granulation and inlay. In many cases, only traces of inlay remain. Some gems changed in color in the process of degradation, and currently look grey. Micro-samples for the research were selected from the crumbling fragments of inlay obtained in the process of restoration of the item. Modern natural scientific methods allow studying the material component of the objects of cultural heritage. The identification procedure is now available even based on the remaining particles with characteristic sizes that do not exceed tens of microns. Within the framework this research, the author examined the possibility of selecting such micro-samples with subsequent identification. Application of the Raman spectroscopic technique allowed examining the selected micro-samples on the next stage. The complementary methods imply Fourier-transform infrared spectroscopy for studying organic substances the inlay was attached to.

scholarly journals Synthesis and crystal structure of a 6-chloronicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bipyridine

2020 ◽  
Vol 76 (5) ◽  
pp. 599-604
Author(s):  
Nives Politeo ◽  
Mateja Pisačić ◽  
Marijana Đaković ◽  
Vesna Sokol ◽  
Boris-Marko Kukovec
Keyword(s):  
Molecular Structure ◽  
Coordination Polymer ◽  
Three Dimensional ◽  
Polymeric Chain ◽  
Water Molecules ◽  
Sulfate Heptahydrate ◽  
Synthesis And Crystal Structure ◽  
One Dimensional ◽  
Polymeric Chains ◽  
Hydrogen Bonded

A 6-chloronicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4′-bipyridine (4,4′-bpy), namely, catena-poly[[[tetraaquanickel(II)]-μ-4,4′-bipyridine-κ2 N:N′] bis(6-chloronicotinate) tetrahydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4′-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate heptahydrate, 6-chloronicotinic acid and 4,4′-bipyridine in a mixture of water and ethanol. The molecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4′-bpy)(H2O)4]2+} n cation, two 6-chloronicotinate anions and four water molecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octahedrally coordinated by four water molecule O atoms and by two 4,4′-bipyridine N atoms in the trans position. The 4,4′-bipyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending along the b-axis direction. In the extended structure of 1, the polymeric chains of {[Ni(4,4′-bpy)(H2O)4]2+} n , the 6-chloronicotinate anions and the water molecules of crystallization are assembled into an infinite three-dimensional hydrogen-bonded network via strong O—H...O and O—H...N hydrogen bonds, leading to the formation of the representative hydrogen-bonded ring motifs: tetrameric R 2 4(8) and R 4 4(10) loops, a dimeric R 2 2(8) loop and a pentameric R 4 5(16) loop.

scholarly journals Diosgenin hemihydrate

2012 ◽  
Vol 68 (8) ◽  
pp. o2357-o2357 ◽  
Author(s):  
María-Guadalupe Hernández Linares ◽  
Sylvain Bernès ◽  
Marcos Flores-Alamo ◽  
Gabriel Guerrero-Luna ◽  
Anselmo A. Martínez-Gallegos
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Dimethyl Sulfoxide ◽  
Starting Material ◽  
Water Molecules ◽  
Asymmetric Unit ◽  
Acta Cryst ◽  
X Ray ◽  
Hydroxy Groups ◽  
Hydrogen Bonded

Diosgenin [or (22R,25R)-spirost-5-en-3β-ol] is the starting material of the Marker degradation, a cheap semi-synthesis of progesterone, which has been designated as an International Historic Chemical Landmark. Thus far, a single X-ray structure for diosgenin is known, namely its dimethyl sulfoxide solvate [Zhanget al.(2005).Acta Cryst.E61, o2324–o2325]. We have now determined the structure of the hemihydrate, C27H42O3·0.5H2O. The asymmetric unit contains two diosgenin molecules, with quite similar conformations, and one water molecule. Hydroxy groups in steroids and water molecules form O—H...O hydrogen-bondedR54(10) ring motifs. Fused edge-sharingR(10) rings form a backbone oriented along [100], which aggregates the diosgenin molecules in the crystal structure.

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