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On the Theory of Shifts and Broadening of Electronic Spectra of Polar Solutes in Polar Media
When a polar‐solute molecule undergoes an electronic transition and forms a state of different polarity, the Franck—Condon principle shows that the new system is first formed in a nonequilibrium thermodynamic state. An expression for the spectral shift and broadening by a series of solvents of differing polarity is derived in the present paper in terms of thermodynamic properties of certain equilibrium distribution systems. For this purpose use is made of a recent particle description of nonequilibrium and equilibrium polar media, which emphasizes functional dependence and avoids, thereby, the usual more specific assumptions. A relation between the broadening and the shift is then deduced under certain conditions. Expressions are also derived for the effect of pressure and temperature on the shift, in terms of the polar contribution to the volume and entropy of solvation, respectively, and for the influence of applied electrical fields. An expression is obtained for the solvent‐reversal shift of Brooker in terms of the polarizability difference of the initial and final states of the solute. Introduction of more specific assumptions is then made for purposes of comparison with earlier works, which constitute special cases of the present one, and for estimation of dipole moments and polarizabilities of excited states from spectral and electrical shifts
On the space of elliptic genera
Invariance under modular transformations and spectral flow restrict the
possible spectra of superconformal field theories (SCFT). This paper presents a
technique to calculate the number of constraints on the polar spectra of
N=(2,2) and N=(4,0) SCFT's by analyzing the elliptic genus. The polar spectrum
corresponds to the principal part of a Laurent expansion derived from the
elliptic genus. From the point of view of the AdS_3/CFT_2 correspondence, these
are the states which lie below the cosmic censorship bound in classical
gravity. The dimension of the space of elliptic genera is obtained as the
number of coefficients of the principal part minus the number of constraints.
As an additional illustration of the technique, the constraints on the spectrum
of N=4 topologically twisted Yang-Mills on CP^2 are discussed.Comment: 31 pages, published versio
An electric charge has no screw sense--a comment on the twistfree formulation of electrodynamics by da Rocha & Rodrigues
Da Rocha and Rodigues (RR) claim (i) that in classical electrodynamics in
vector calculus the distinction between polar and axial vectors and in exterior
calculus between twisted and untwisted forms is inappropriate and superfluous,
and (ii) that they can derive the Lorentz force equation from Maxwell's
equations. As to (i), we point out that the distinction of polar/axial and
twisted/untwisted derives from the property of the electric charge of being a
pure scalar, that is, not carrying any screw sense. Therefore, the mentioned
distinctions are necessary ingredients in any fundamental theory of
electrodynamics. If one restricted the allowed coordinate transformations to
those with positive Jacobian determinants (or prescribed an equivalent
constraint), then the RR scheme could be accommodated; however, such a
restriction is illegal since electrodynamics is, in fact, also covariant under
transformations with negative Jacobians. As to (ii), the "derivation" of the
Lorentz force from Maxwell's equations, we point out that RR forgot to give the
symbol F (the field strength) in Maxwell's equations an operational meaning in
the first place. Thus, their proof is empty. Summing up: the approach of RR
does not bring in any new insight into the structure of electrodynamics.Comment: Added answer to da Rocha & Rodrigues arXiv:0912.212
Basic differential forms for actions of Lie groups
A section of a Riemannian -manifold is a closed submanifold
which meets each orbit orthogonally. It is shown that the algebra of
-invariant differential forms on which are horizontal in the sense that
they kill every vector which is tangent to some orbit, is isomorphic to the
algebra of those differential forms on which are invariant with
respect to the generalized Weyl group of this orbit, under some condition.Comment: 10 pages, ESI Preprint 87, AmSTe
Investigating nano-structuring within imidazolium ionic liquids: A thermodynamic study using photochromic molecular probes
Following previous studies involving the thermal relaxation of spirocyclic compounds we
extended our studies to investigate the formation of nano-structured domains in ionic liquids
(ILs). Two compounds, spiropyran (BSP) and spirooxazine (SO) were added to imidazolium
cation based ionic liquids with increasing chain lenghts (C2 –C12). Increasing side-chain length
was found to have only minor effects on the rate of thermal relaxation of BSP and SO. BSP was
found to be a suitable probe molecule as linear correlations in parameters were observed for this
compound. This is believed to be due to the fact that BSP-IL interactions were based on hydrogen
bonding between MCBSP and the cation compared to MCSO which is limited to electrostatic
interactions thus enhancing the sensitivity of MCBSP to the charged polar regions. Increasing the
side-chain of the cation resulted in slight increases in MC-BSP activation energy from 96.93
kJ.mol-1 in [C4mIm][NTf2] to 105.27 kJ.mol-1 in [C12mIm][NTf2]. MC-BSP S‡ and H‡ values
also increased with increasing side-chain. Expansion and dispersion of polar regions due to
increasing non-polar interactions may be enhanced by introduction of the bulky probe molecule.
The resulting reorganisation of the system produced positive entropies of activation, 13.79 J.K-
1.mol-1 for C4mIm to 46.15 J.K-1.mol-1 for C12mIm, following an increase in disorder due to probe
dye closure from MC to BSP and migration of dye to regions of preferential solvation. The ability
for spirocyclic compounds to form both polar and non-polar isomers resulted in the ability to
analyse both solvent regions using a single probe dye. Ground state equilibrium, Ke, examined
non-polar regions of the IL while equilibrium of activation, K‡, examined the polar regions. A
linear response to side chain length to equilibrium of activation was believed to be due to the fact
that polar regions were possibly expanding due to increasing influence of non-polar side chain
interactions upon the over solvent structure. The result of such reordering and dispersion of polar
regions reduces solvent-solute interactions which increases rate of MC-BSP relaxation
A study of magnetic storms and auroras
New notations for magnetic disturbance fields are proposed, based on
the theoretical consideration of the electric current systems by which
they are produced.
A typical magnetic storm begins suddenly when the onrush of the front
of the solar gas is halted by the earth's magnetic field. This effect
(DCF field) is most markedly observed as a sudden increase of the horizontal
component of the earth's field (the storm sudden commencement,
abbreviated to ssc)— like a step function. In many cases, however, the
change of the field during the ssc is more complicated, and different at
different places. Such a complexity superposed on the simple increase
(DCF) is ascribed to a complicated current system generated in the polar
ionosphere (DP current). It is found that the changes of electromagnetic
conditions in the polar regions are communicated, without delay, to lower
latitudes, even down to the equatorial regions. It is inferred that the
equatorial jet is affected by such a change and produces the abnormal
enhancement of ssc along the magnetic dip equator.
From the extensive analysis of several magnetic storms that occurred
during the IGY and IGC, it is suggested that the capture of the solar
particles in the outer geomagnetic field occurs when irregularities
(containing tangled magnetic fields and high energy protons) embedded in
the solar stream, impinge on the earth.. Thus the development of a magnetic
storm depends on the distribution of such irregularities in the stream.
The motions and resulting currents and magnetic fields of such "trapped"
solar particles are studied in detail for a special model. It is inferred
that a large decrease (DR field) must follow the initial increase; it is
ascribed to the ring current produced by such motion of solar protons oi
energy of order 500 Kev. It is proposed that during the storm there
appears a transient 'storm-time1 belt well outside the outer radiation
belt.
It is predicted that the earth's magnetic field is reversed in
limited regions when the ring current is appreciably enhanced. This
involves the formation of neutral lines there. These may be of two
kinds, called X lines or 0 lines according as they are crossed or encircled
by magnetic lines of force. These may be entirely separated or
may be joined to form a loop, called an OX loop. It is shown that one
of them, the X line, which is connected with the auroral ionosphere by
the lines of force, could be the proximate source of th<e particles that
produce the aurora polaris. By postulating the existence of such X-type
neutral lines at about 6 earth radii, an explanation is obtained of the
detailed morphology of the aurora. This includes the auroral zones and
their changes, the nighttime peak occurrence of auroras, their thin
ribbon-like structure and their multiplicity, their diffuse and active
forms and the transition between them (break-up) the required electron
and proton flux, and the ray and wavy structures.
Among the most important phenomena associated with the sudden change
of the aurora from the diffuse to the active form are the simultaneous
appearance of the auroral electrojet and the resulting polar magnetic
disturbances (DP sub-storms). Several typical DP sub-storms are studied
in detail. It is concluded that a westward auroral jet is produced by a
southward electric field. It is shown that an instability of the sheetbeam
issuing from along the X-type neutral line can produce a southward
electric field of the required intensity. The southward electric field
produces an eastward motion of the electrons in the ionosphere. This may
be identified with the eastward motion of an active aurora and with the
westward auroral electrojet.
Besides such large changes- of the field, there often appear various
quasi-sinusoidal changes of the field, much less intense. They are
supposed to be hydromagnetic waves, some of which are generated in the
outer atmosphere and propagated through the ionosphere, where a certain
amount of their energy is dissipated. It is concluded however that Such
a dissipation is not sufficient to produce any appreciable heating of the
ionosphere.Chapter I The electromagnetic environment of the earth : The solar system in the Galaxy ; The sun and the interplanetary space ; The outer atmosphere, the Van Allen radiation belts and the ionosphere ; The earth’s permanent magnetic field ; Introduction to geomagnetic storms and auroras ; The analysis of the earth’s magnetic field – Chapter II The sudden commencement of magnetic storms : Introduction ; The studies of Sc and Si at individual observations ; A theory of the Sc of magnetic storms ; Transmission of the Sc from the inner boundary of the solar steam to the earth’s surface ; The sudden commencement DP currents – Chapter III The ring current and the van allen radiation belts : Introduction ; The motion of charged particles in the earth’s dipole magnetic field ; Electric currents in an ionized gas (general formulae) ; The steady ring current in a dipole field ; The magnetic field produced by the ring current ; The main phase of magnetic storms ; The ring current belt ; Discussion – Chapter IV A neural line discharge theory of the aurora Polaris : Introduction ; The formation of a neutral line ; The motions of charged particles close to a neutral line ; The auroral zones ; Particle injection associated with arcs ; Rayed arcs ; Instabilities of auroras – Chapter V Polar magnetic disturbances : Introduction ; The polar magnetic disturbances of 5 to 6 December 1958 (College, Alaska) ; The polar magnetic disturbances of 29 September 1957 (Worldwide) ; The polar magnetic disturbances of 23 September
1957 ; The eastward motion of auroras and the electric field of polar magnetic disturbances ; The origin of the electric field of polarmagnetic disturbances – Chapter VI Hydromagnetic waves in the ionosphere : Introduction ; Ionospheric heating by hydromagnetic waves connected with geomagnetic micropulsations – Acknowledgements -- ReferencesYe
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