scholarly journals Vibrational Stark Fields in Carboxylic Acid Dimers

2022 ◽  
Author(s):  
Manjusha Boda ◽  
G Naresh Patwari
Keyword(s):  
Carboxylic Acid ◽  
Electric Field ◽  
Secondary Effects ◽  
Frequency Shifts ◽  
Tuning Rate ◽  
Double Proton Transfer ◽  
Stabilization Energies ◽  
Stretching Vibrations ◽  
The Difference ◽  
Weakly Dependent

Carboxylic acids form exceptionally stable dimers and have been used to model proton and double proton transfer processes. The stabilization energies of the carboxylic acid dimers are very weakly dependent on the nature of the substitution. However, the electric field experienced by the OH group of a particular carboxylic acid is dependent more on the nature of the substitution on the dimer partner. In general, the electric field was higher when the partner was substituted with electron-donating group and lower with electron-withdrawing substituent on the partner. The Stark tuning rate (∆μ) of the O–H stretching vibrations calculated at the MP2/aug-cc-pVDZ level was found to be weakly dependent on the nature of substitution on the carboxylic acid. The average Stark tuning rate of O–H stretching vibrations of a particular carboxylic acid when paired with other acids was 5.7 cm–1 (MV cm–1)–1, while the corresponding average Stark tuning rate of the partner acids due to a particular carboxylic acid was 21.9 cm–1 (MV cm–1)–1. The difference in the Stark tuning rate is attributed to the primary and secondary effects of substitution on the carboxylic acid. The average Stark tuning rate for the anharmonic O–D frequency shifts is about 40-50% higher than the corresponding harmonic O–D frequency shifts calculated at B3LYP/aug-cc-pVDZ level, much greater than the typical scaling factors used, indicating the strong anharmonicity of O–H/O–D oscillators in carboxylic acid dimers. Finally, the linear correlation observed between pKa and the electric field was used to estimate the pKa of fluoroformic acid to be around 0.9.

scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

Shape of piezoelectric hysteresis loop for non-ferroelastic switching

2003 ◽  
Vol 784 ◽  
Author(s):  
A. K. Tagantsev ◽  
P. Muralt ◽  
J. Fousek
Keyword(s):  
Thin Films ◽  
Electric Field ◽  
Hysteresis Loop ◽  
Single Crystals ◽  
Applied Electric Field ◽  
Piezoelectric Coefficient ◽  
Hysteresis Loops ◽  
Simple Theory ◽  
The Difference

ABSTRACTA simple theory for the shape of the piezoelectric hysteresis loops (piezoelectric coefficient d vs. applied electric field E) is developed for the case of non-ferroelelastic 180° switching in ferroelectrics. The theory provides explanations for specific features of piezoelectric hysteresis loops, which have been observed in single crystals, thin films and in ceramics in particular. The piezoelectric coefficient may show a “hump”, i.e. when E decreases from the tip of the loop down to zero, d passes through a maximum, and a “nose”, i.e. a self-crossing of the loop close to its tips. The theory also explains the difference in the coercive fields seen in the polarization and piezoelectric loops.

Scaling Behavior of Dynamic Hysteresis in Hard PZT Bulk Ceramics under Influence of Compressive Stress

2008 ◽  
Vol 55-57 ◽  
pp. 281-284 ◽  
Author(s):  
N. Wongdamnern ◽  
Athipong Ngamjarurojana ◽  
Supon Ananta ◽  
Yongyut Laosiritaworn ◽  
Rattikorn Yimnirun
Keyword(s):  
Energy Dissipation ◽  
Electric Field ◽  
Mechanical Stress ◽  
Compressive Stress ◽  
Power Law ◽  
Field Amplitude ◽  
Electric Field Amplitude ◽  
Bulk Ceramic ◽  
Compressive Stresses ◽  
The Difference

Effects of electric field-amplitude and mechanical stress on hysteresis area were investigated in partially depoled hard PZT bulk ceramic. At any compressive stress, the hysteresis area was found to depend on the field-amplitude with a same set of exponents to the power-law scaling. Consequently, inclusion of compressive stresses into the power-law was also obtained in the form of < A – Aσ=0 > α E05.1σ1.19 which indicated the difference of the energy dissipation between the under-stress and stress-free conditions.

Smectic C to Cubic Phase Transition of 4′-n-Docosyloxy-3′-nitrobiphenyl-4-carboxylic Acid (ANBC-22) and Alternating-Current Electric Field Effect

2009 ◽  
Vol 113 (3) ◽  
pp. 640-646 ◽  
Author(s):  
Shoichi Kutsumizu ◽  
Kouhei Hosoyama ◽  
Makoto Yamada ◽  
Katsufumi Tanaka ◽  
Ryuichi Akiyama ◽  
...  
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Electric Field ◽  
Field Effect ◽  
Alternating Current ◽  
Cubic Phase ◽  
Electric Field Effect ◽  
Smectic C ◽  
Current Electric Field

scholarly journals Probing the electric field across thylakoid membranes in cyanobacteria

2019 ◽  
Vol 116 (43) ◽  
pp. 21900-21906 ◽  
Author(s):  
Stefania Viola ◽  
Benjamin Bailleul ◽  
Jianfeng Yu ◽  
Peter Nixon ◽  
Julien Sellés ◽  
...  
Keyword(s):  
Electric Field ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Transport Pathways ◽  
Electrochromic Shift ◽  
Ideal Tool ◽  
Bona Fide ◽  
The Difference ◽  
And Function

In plants, algae, and some photosynthetic bacteria, the ElectroChromic Shift (ECS) of photosynthetic pigments, which senses the electric field across photosynthetic membranes, is widely used to quantify the activity of the photosynthetic chain. In cyanobacteria, ECS signals have never been used for physiological studies, although they can provide a unique tool to study the architecture and function of the respiratory and photosynthetic electron transfer chains, entangled in the thylakoid membranes. Here, we identified bona fide ECS signals, likely corresponding to carotenoid band shifts, in the model cyanobacteria Synechococcus elongatus PCC7942 and Synechocystis sp. PCC6803. These band shifts, most likely originating from pigments located in photosystem I, have highly similar spectra in the 2 species and can be best measured as the difference between the absorption changes at 500 to 505 nm and the ones at 480 to 485 nm. These signals respond linearly to the electric field and display the basic kinetic features of ECS as characterized in other organisms. We demonstrate that these probes are an ideal tool to study photosynthetic physiology in vivo, e.g., the fraction of PSI centers that are prebound by plastocyanin/cytochrome c6 in darkness (about 60% in both cyanobacteria, in our experiments), the conductivity of the thylakoid membrane (largely reflecting the activity of the ATP synthase), or the steady-state rates of the photosynthetic electron transport pathways.

The Infrared Absorption Spectra of Some Samarium Diketo-ester Complexes

1970 ◽  
Vol 25 (2) ◽  
pp. 139-141 ◽  
Author(s):  
S. P. Tandon ◽  
P. C. Mehta
Keyword(s):  
Coordination Number ◽  
Absorption Spectra ◽  
Infrared Absorption ◽  
Relative Frequency ◽  
Methyl Acetoacetate ◽  
Frequency Shifts ◽  
Modes Of Vibration ◽  
Infrared Absorption Spectra ◽  
Stretching Vibrations ◽  
First Time

Infrared absorption spectra of some four- and five-coordinated (ethyl 1-methyl acetoacetate) complexes of trivalent samarium have been studied in the region 4000 - 250 cm-1 for the first time. About twenty bands in each chelate have been observed and assigned to different modes of vibration. A study of relative frequency shifts of CO stretching vibrations reveals that the metal-oxygen bonds in all the complexes are nearly of the same strength. The vibrational frequencies, with few exceptions, are found to be nearly independent of the coordination number of the metal.

The Lobe Structure in Ice Accreted on an Aluminium Conductor in The Presence of a Dc Electric Field

1983 ◽  
Vol 4 ◽  
pp. 228-235 ◽  
Author(s):  
Luan C. Phan ◽  
Jean-Louis Laforte ◽  
Du D. Nguyen
Keyword(s):  
Electric Field ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Air Bubbles ◽  
Experimental Conditions ◽  
Charged Droplets ◽  
Water Drops ◽  
The Difference ◽  
Negative Electric Field ◽  
Corona Wind

Supercooled droplets of 38 μm mean volume diameter are accreted on a smooth aluni mum cylinder of 3.15 cm in diameter in order to study the effect of an electrostatic field upon ice formation on a power-line conductor. The results obtained show that ice grown in the presence of an applied negative field of 15 kV cm−1 exhibits a cusped-lobe structure characterized by surfacial outward knobs, convex rings of fine air bubbles and radial lines of large air bubbles; in the same conditions, a positive electric field of 15 kV cm−1 does not produce such lobe features. On the other hand, accretion tests performed in the absence of an electric field with a 33 μm droplet spectrum show that the well-developed cusped-lobe structure appears in ice at low ambient temperature and air velocity. In the present experimental conditions, the formation of cusped lobes observed in the presence of a negative electric field could be explained by a decrease in the temperature of the deposit due to a reduction of impact velocity of the charged droplets and/or an increase in the local heat-transfer coefficient at the surface of the ice accretion. Corona wind from ice points, always in the opposite direction to the impinging droplets, may also reduce their impact velocities. In addition, corona wind and roughness of the surface may contribute to a better evacuation of the latent heat and thus decrease the deposit temperature. The difference between the effects of a negative DC field and those of a DC positive field of the same strength comes from a stronger ionization intensity and/or a stronger deformation of water drops in the negative electric field.

Comparison between Ferromagnetic and Ferroelectric Optical Switch Devices in Terms of the Response to the Electric Field

2018 ◽  
Vol 23 ◽  
pp. 1-7
Author(s):  
Rabi Noori Hammudi ◽  
Sudad Salman Al-Bassam ◽  
Rawa Khalil Ibrahim ◽  
Aseel Ibrahim Mahmood ◽  
Peter Kopčanský ◽  
...  
Keyword(s):  
Magnetic Material ◽  
Electric Field ◽  
Response Time ◽  
Applied Electric Field ◽  
Optical Switch ◽  
Ferroelectric Material ◽  
Optical Effect ◽  
Constituent Material ◽  
Electro Optic ◽  
The Difference

In this work we have studied the electro-optical effect of two types of ferronematic nanoparticles. The first sample doped with magnetic material Fe3O4 and the second sample doped with a ferroelectric material SbSI. The difference in the two types of material that has been vaccinated led to different values of electro-optic properties because of the different susceptibility of materials. We have noticed that the material SbSI was more responsive to the applied electric field due to the nature of the constituent material (electric material) than the Fe3O4 ferromagnetic. The response time for the material SbSI is less than the response time of the ferromagnetic Fe3O4, that led to make the material SbSI best in the optical switch applications.

A review of the October 21, 1989 red aurora seen in Japan and from the AKEBONO (EXOS-D) satellite

1992 ◽  
Vol 70 (7) ◽  
pp. 488-499 ◽  
Author(s):  
T. Oguti
Keyword(s):  
Electric Field ◽  
Magnetic Storm ◽  
Auroral Oval ◽  
Low Latitude ◽  
Terrestrial Environment ◽  
Acceleration Mechanism ◽  
Auroral Substorm ◽  
Field Fluctuations ◽  
The Difference ◽  
Auroral Expansion

Observations of the October 21, 1989 red aurora from the ground and AKEBONO satellite are reviewed mainly on the topics presented at the workshop on the aurora, held in Solar Terrestrial Environment Laboratory on January 17–18, 1991. Electric-field fluctuations associated with the auroral oval during the observation, together with auroral green-rayed structures embedded in the red veil strongly suggest that some electron acceleration mechanism was operative in the particle precipitation. Therefore this was not a typical stable auroral red (SAR) arc. This red aurora was most likely located at a low-latitude portion of an expansion aurora during an auroral substorm. The geomagnetic conditions at the time of the aurora were quite similar to those during the occurrence of a SAR arc. It occurred during a susbtorm that broke out at the maximum Dst (disturbance with storm time) phase of a magnetic storm, with an auroral expansion initiated from low latitude on a well-expanded auroral oval. The difference in conditions between a typical SAR arc and this red aurora with green-ray structures is to be studied further.

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