Author
Purnendranath Sen
Bio: Purnendranath Sen is an academic researcher. The author has contributed to research in topics: Polarizability & Sublimation (phase transition). The author has an hindex of 3, co-authored 10 publications receiving 19 citations.
Papers
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TL;DR: Using a free-electron model for the πelectron system in benzene, the electronic quadrupole moment has been calculated to be 2629 × 10−26 esu as discussed by the authors.
Abstract: Using a free‐electron model for the π‐electron system in benzene the electronic quadrupole moment has been calculated to be 2629 × 10−26 esu which is in fair agreement with the experimental value of 3486 × 10−26 esu Considering the molecular interaction to be quadrupolar in origin for benzene crystal the sublimation energy was calculated to be 1064 kcal/mole which is in good agreement with the experimental value of 1067 kcal/mole
8 citations
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TL;DR: In this article, the triplet-state lifetime of benzene for the 330 mμ band has been estimated to be about 36 sec, which compares favourably with the corrected experimental value of 30 sec.
Abstract: Using the free-electron model the triplet-state lifetime of benzene for the 330 mμ band has been estimated to be about 36 sec, which compares favourably with the corrected experimental value of 30 sec. It has also been established that the perturbing singlet must be a π-σ singlet rather than a π-π singlet.
3 citations
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TL;DR: The charge on each atom of some ethers and chloro-substituted ethers, their dipole moments and the quadrupole coupling constants of the chloroethers have been calculated with the method suggested by Del Re as mentioned in this paper.
Abstract: The charge on each atom of some ethers and chloro-substituted ethers, their dipole moments and the quadrupole coupling constants of the chloroethers have been calculated with the method suggested by Del Re. There appears to be an intimate connection between the charge density on the oxygen atoms and the capacity of forming hydrogen bond.
3 citations
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TL;DR: In this article, the hyperpolarizability of benzene was calculated using a free-electron model for the π -electron system and the results showed that only the components γ zzzz, γ xxxx, γ yyyy and γ nzzz are non-zero.
Abstract: The hyperpolarizabilities of benzene have been calculated using a free-electron model for the π-electron system. The first hyperpolarizability is identically zero. For the second hyperpolarizability only the components γ zzzz ; γ xxxx ; γ yyyy ; γ zzxx ; γ zzyy ; γ xxyy are non-zero. Some of these γ quantities show dispersion near the characteristic absorption band of the benzene molecule. The polarizability α of the π-electron system also shows similer dispersion.
2 citations
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TL;DR: In this article, a theory of quantum-mechanical collective motion for π-electron systems in aromatic hydrocarbons is presented. But it is only applicable to two-dimensional collective oscillations, not only longitudinal oscillations but also surface oscillations similar to an incompressible fluid.
Abstract: Publisher Summary This chapter discusses Tomonaga gas model, collective oscillation in π -electron system in aromatic hydrocarbons and collective oscillation in linear conjugated molecule. There are two methods of approach in the treatment of quantum-mechanical collective motions. Tomonaga has developed a theory of collective motion that is applicable to a large class of dynamical systems provided the system is actually capable of performing collective motions, not only longitudinal oscillation but also surface oscillations similar to that of an incompressible fluid. This theory is a natural generalization of the use of center-of-mass coordinates to describe translational motions and to separate them for the internal relative motions of the system. In the free-electron model for the pi-electrons in aromatic hydrocarbons the electrons are assumed to move freely along the circumference of a circle in a zero potential field. The pi-electrons in effect form a two-dimensional electron gas. Because of the electrostatic repulsion between the electrons, a dynamical system consisting of N electrons will strongly resist compression of the system. The electrons will move in such a way that the density undergoes no change because in this motion the change of potential energy will be smallest. The motion is most likely to occur in systemisa two-dimensional collective oscillation. It is surmised, therefore, that the quantum-mechanical collective motion proposed by Tomonaga will be applicable to the pi-electron system in aromatic hydrocarbons.
1 citations
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TL;DR: This paper deals with the analysis of the steric and chiral requirements of protein secondary structures and establishes a quantitative correlation between structure periodicity and the experimental values of the backbone residual dipolar couplings.
Abstract: A new approach to the interpretation of residual dipolar couplings for the regular secondary structures of proteins is presented. This paper deals with the analysis of the steric and chiral requirements of protein secondary structures and establishes a quantitative correlation between structure periodicity and the experimental values of the backbone residual dipolar couplings. Building on the recent interpretation of the periodicity of residual dipolar couplings in alpha-helices (i.e., "dipolar waves"), a general parametric equation for fitting the residual dipolar couplings of any regular secondary structure is derived. This equation interprets the modulation of the residual dipolar couplings' periodicity in terms of the secondary structure orientation with respect to an arbitrary reference frame, laying the groundwork for using backbone residual dipolar couplings as a fast tool for determining protein folding by NMR spectroscopy.
41 citations
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31 citations
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TL;DR: In this paper, the second harmonic generation by multipolar substances placed in a DC or AC electric field is related not only with nonlinear electronic polarisation of molecules but essentially with orientation of the electric molecular multipoles and their interaction in the condensed state.
26 citations
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TL;DR: In this paper, the authors extended the molecular theory of the smectic $B$ and $H$ phases by including the phenyl-phenyl interaction in addition to the dipole-dipole potential used previously.
Abstract: The molecular theory of the smectic $B$ and $H$ phases is extended to the smectic $E$ and VI phases by including the phenyl-phenyl interaction in addition to the dipole-dipole potential used previously. This phenyl-phenyl interaction contains quadrupole-quradrupole, dispersive, and exchange terms. The possibility of both dipolar and "herringbone" order is considered in the self-consistent-field approximation. Four phases are found, all with a two-dimensional hexagonal lattice assumed: (1) a disordered phase (smectic $B$); (2) an oriented phase in which dipoles align (smectic $H$); (3) a herringbone phase with phenyl groups ordered (smectic $E$); (4) and a herringbone phase with both phenyl groups and dipoles ordered (smectic VI). In the phases with dipolar order the director is tilted with respect to the normal to the plane. The transitions vary in order. The temperature dependence of the order parameters, entropy, and specific heat are computed.
25 citations