Study of electric potentials across a moving solid-liquid interface

The electric potential across a melting sample of pure lead was measured as a function of time. A difference of the order of a few hundred microvolts was seen between the measured values of the potential and those calculated using the temperature gradients and the thermopowers of the solid and the liquid phases. This difference persists as long as the solid-liquid interface moves and is attributed to the Galvani potential present at the solid-liquid interface. It is suggested that such measurements can be used to obtain the value of the Fermi energy for liquids.     

C?C Cross‐Coupling Reactions of O6‐Alkyl‐2‐Haloinosine Derivatives and a One‐Pot Cross‐Coupling/O6‐Deprotection Procedure

Reaction conditions for the C? C cross‐coupling of O⁶‐alkyl‐2‐bromo‐ and 2‐chloroinosine derivatives with aryl‐, hetaryl‐, and alkylboronic acids were studied. Optimization experiments with silyl‐protected 2‐bromo‐O⁶‐methylinosine led to the identification of [PdCl₂(dcpf)]/K₃PO₄ in 1,4‐dioxane as the best conditions for these reactions (dcpf=1,1′‐bis(dicyclohexylphosphino)ferrocene). Attempted O⁶‐demethylation, as well as the replacement of the C‐6 methoxy group by amines, was unsuccessful, which led to the consideration of Pd‐cleavable groups such that C? C cross‐coupling and O⁶‐deprotection could be accomplished in a single step. Thus, inosine 2‐chloro‐O⁶‐allylinosine was chosen as the substrate and, after re‐evaluation of the cross‐coupling conditions with 2‐chloro‐O⁶‐methylinosine as a model substrate, one‐step C? C cross‐coupling/deprotection reactions were performed with the O⁶‐allyl analogue. These reactions are the first such examples of a one‐pot procedure for the modification and deprotection of purine nucleosides under C? C cross‐coupling conditions.     

Epr studies of divalent manganese ions in magnesium maleate dihydrate single crystals

Abstract

An EPR study of Mn²⁺ ions doped in single crystals of Dihydrate Magnesium Maleate has been carried out at room temperature at X-band. From the observed spectra, spin-Hamiltonian parameters have been evaluated. Mn²⁺ ions have been found to enter the lattice interstitially.     

RF pulse response of a system of 1 = 32 nuclei in the presence of quadrupole splitting

The rf pulse response of a I = $\text{3}\text{2}$ spin system experiencing first order quadrupole splitting has been studied using the density matrix method. An expression has been derived for the transverse magnetization caused by a pulse of length τ_p applied at the centre line frequency. From this expression, the length of pulse (τ_p)_max that produces maximum transverse magnetization has been calculated as a function of the ratio of the quadrupole splitting to the pulse amplitude. Very good agreement is found with experimental values of (τ_p)_max for ²³Na in a single crystal of NaNO₃.     

Supermodes of chiral photonic filters with combined twist and layer defects

We consider the circularly polarized localized modes of chiral photonic structures with combined central twist and isotropic layer defects. The general filter is shown to suffer from anomalous remittance and saturation of linewidth as the thickness of the structure is increased. However, by choosing parameters that phase match the elements of the round-trip matrix of the isotropic layer defect, we demonstrate the existence of supermodes that maintain exceptional purity of polarization state and exponential decrease in linewidth as the thickness is increased.     

Absorption spectrum of Cr3+ ion doped in lithium ammonium sulphate single crystal

The absorption spectrum of Cr³⁺ ion doped in lithium ammonium sulphate single crystal has been studied both at room (300 K) and liquid nitrogen (77 K) temperatures. From the nature and position of the observed bands, O_h symmetry is assumed for the ion. The spectroscopic parameters derived for the ion in the crystal at 77 K are Dq = 1655 cm^?1, B = 735 cm^?1 and C/B = 4.4     

Absorption spectra of Ni2+ in (NH4)2Mg(SO4)2·6H2O and Co2+ in Na2Zn(SO4)2·4H2O

Optical absorption spectra of Ni²⁺ in (NH₄)₂Mg(SO₄)₂·6H₂O and Co²⁺ in Na₂Zn(SO₄)₂·4H₂O single crystals have been studied at room and liquid nitrogen temperatures. From the nature and position of the observed bands, a successful interpretation could be made assuming octahedral symmetry for both the ions in the crystals. The splitting observed for ${}^3\text{T}{}_{\mathrm{1g}}\text{(F)}$ band in Ni²⁺ and ${}^4\text{T}{}_{\mathrm{2g}}\text{(F)}$ band in Co²⁺ at liquid nitrogen temperature have been explained as due to spin-orbit interaction. The extra band observed at 16,325 cm^-1 in the case of Ni²⁺ at low temperature has been interpreted to be the superposition of vibrational mode of SO^2-₄ radical on ${}^3\text{T}{}_{\mathrm{1g}}\text{(F)}$ band. The observed band positions in both the crystals have been fitted with four parameters B, C, Dq and ζ.     

True potential energy curves,r-centroids and franck-condon factors of a few transition metal diatomic molecules

The true potential energy curves for some electronic states of CuF, CuO, CuSe and CuTe molecules have been constructed by the method of Lakshman and Rao (RKR method as modified by Lakshman and Rao). The ground-state dissociation energies evaluated by the method of curve fitting using the H-H function agree well with the values reported earlier. Ther-centroids and Franck-Condon factors for various band systems of the above diatomic molecules have been computed.     

Absorption spectrum of Ni2+ doped in NH4Br single crystal

The optical absorption spectrum of Ni²⁺ doped in NH₄Br single crystals has been studied at room and liquid-air temperatures. The observed ambient bands at 6300, 11,600, 13,400, 18,500, and 20,000 cm^–1 have been assigned, respectively, to the transitions³ A ₂(F) ³ T ₂(F),³ T ₁(F),¹ E(D),¹ T ₂(D and³ T ₁(P). The crystal field parameters evaluated areD _q=630 cm^–1,B=850 cm^–1, andC=3600 cm^–1. In assigning the location of Ni²⁺ ions within the lattice, evaluations are made of the (limited) extant comparable data. It is then concluded that Ni²⁺ enters an octahedral interstitial, rather than a substitutional, site. It is surrounded by four bromide ions, in a plane, with two polarized water molecules at the opposing fifth and sixth positions.