Indian Journal of Pure and Applied Physics
___________________________________________________________________________________
VOLUME 40
NUMBER 1
JANUARY 2002
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CONTENTS
Nuclear Physics
5
40K, 137Cs and 232Th activities in Brazilian milk samples measured by gamma ray spectrometry
F L Melquiades* & C R Appoloni
Atomic and Molecular Physics
12
Spectroscopic study of pentacene assembled in Langmuir-Blodgett film mixed with stearic acid
Somobrata Acharya, Tapan Kr Parichha & G B Talapatra*
Vibational assignments of 2,6-di(p-methoxyphenyl)-3-methyl piperidone, 2,6-di(p-methyl phenyl)-3methyl piperidone, 2,6-di(o-hydroxy phenyl)-3-methyl piperidone and 1-methyl-2,6 (p-methoxy
phenyl) piperidone
T Chithambarathanu, V Umayorubagan & V Krishnakumar*
Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics
Ultrasonic studies on charge transfer complexes of iodine with certain aromatic compounds in n-hexane
solution
V Kannappan* & S Kothai
Physics of Gases, Plasmas and Electric Discharges
Unified empirical model for collective oscillations of asymmetric positive space charge sheath
Ram Prakash, A Sarma, C B Dwivedi*, U Deka, B Singha, S Bujarbarua & J C Upadhyaya
Condensed Matter: Structure, Mechanical and Thermal Properties
Evaluation of partial and total structure factors, Bhatia-Thornton correlation functions, compressibility
and diffusion coefficient of Pb-Pd alloy at different compositions and temperatures
Sumita Bandyopadhyay, R Venkatesh & R V Gopala Rao*
Applicability of Van’t Hoff equation in calculation of impurities in liquid crystalline materials
Ravindra Dhar*, R S Pandey & S L Srivastava
Studies of Mn0.5Cr0.5Fe2O4 ferrite by neutron diffraction at different temperatures in the range 768 K  T
 13K
A K M Zakaria*, M A Asgar, F U Ahmed, A K Azad, S M Unus, S K Paranjpe & A Das
Thermally stimulated conductivity and evaluation of some parameters of CaS:Pr phosphors
R N Dubey O N Awasthi, V Singh* & M Tiwari
X-ray analysis of 2-methyl-4-phenyl-3,4-dihydro-quinazolinium chloride
Rajnikant*, V K Gupta, O P Suri & M Lal
Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Micro-crystallographic and spectral response studies of CdSe1-xTex alloyed thin films
PD More, G Shahane, L P Deshmukh*, P N Bhosale, A A Belhekar & M K Dongare
Dielectric relaxation of some rigid polar molecules and their binary mixture in benzene solution
A D Vyas* & V A Rana
____________
*The corresponding author has been indicated by (*) mark in case of papers with more than one author
72
17
24
32
42
46
54
59
62
69
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 5-11
40
K, 137Cs and 232Th activities in Brazilian milk samples
measured by gamma ray spectrometry
F L Melquiades & C R Appoloni
This work deals with the measurement of radioactivity in powdered milk, with high-resolution gamma-ray
spectrometry, using a HPGe detector. Preliminary measurements were accomplished to define the kind of the system shield,
the geometry of the sample recipient, the size of the sampling and the self-absorption correction. It was possible to measure
the radionuclides 40K, 137Cs and 232Th. Tukey’s average comparison test was used to check the repeatability of the
measurements.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 12-16
Spectroscopic study of pentacene assembled in
Langmuir-Blodgett film mixed with stearic acid
Somobrata Acharya, Tapan Kr Parichha & G B Talapatra
Langmuir Blodgett (LB) films of non-amphiphilic pentacene mixed with stearic acid have been prepared
and its photo-physical properties are reported here. Surface pressure versus area-per-molecule isotherms (-A)
at different compositions are measured. Spectroscopic properties (UV-Visible absorption, emission and
Scanning Electron Micrograph) of pentacene in LB film have been reported. The blue-shifted absorption and
red shifted emission suggest the formation of H-type of aggregates.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 72-74
NOTE
Vibrational assignments of 2,6-di(p-methoxy phenyl)-3-methyl
piperidone, 2,6-di(p-methyl phenyl)-3-methyl piperidone,
2,6-di(o-hydroxy phenyl)-3-methyl piperidone and
1-methyl-2,6(p-methoxy phenyl) piperidone
T Chithambarathanu, V Umayorubagan & V Krishnakumar
The FTIR spectra of the title compounds were recorded in the region 400–4000 cm-1 and the detailed
vibrational assignments have been proposed based on the functional group frequency approach.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 17-23
Ultrasonic studies on charge transfer complexes of iodine with certain
aromatic compounds in n-hexane solution
V Kannappan & S Kothai
Ultrasonic velocities, densities and viscosities have been measured in n-hexane solutions containing iodine (acceptor)
and diphenyl (DP), diphenyl amine (DPA) or diphenyl ether (DPE) (donor) at various equimolar concentrations at 303 K.
Acoustical parameters such as adiabatic compressibility (), linear free length (Lf), relaxation time (), free volume (Vf),
molecular interaction parameter (), acoustical impedance (Z), absorption coefficient (/f2), Rao’s constant (R), cohesive
energy (CE), internal pressure (i) and Van der Waal’s constant (a) are evaluated. These parameters indicate the formation
of charge-transfer complexes between iodine and the aromatic compounds. The stability constant (K), the free energy of
activation (G*), the standard free energy of formation (G) values are reported for the donor-acceptor complexes. These
investigations reveal that the stability of the charge transfer complex depends on the structure of the aromatic compound.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 24-31
Unified empirical model for collective oscillations of asymmetric
positive space charge sheath
Ram Prakash, A Sarma, C B Dwivedi, U Deka, B Singha, S Bujarbarua & J C Upadhyaya
Hypothesis for a comprehensible unification of the previous physical models for the collective oscillation dynamics
and its driving mechanism for an asymmetric positive space charge sheath has been proposed. Under diode-like circuit
approximations of the sheath, the asymmetry driven beam-plasma interaction model provides a source mechanism to
produce an internal rf resonator to transform the diode-like sheath into a system of an active oscillator. The LCR
components and the resonant frequency of the equivalent diode-like circuit of the sheath are estimated for real experimental
plasma parameters. The numerical values of the resonant eigen frequency of the equivalent circuit for different grid biasing
voltages are validated against the real experimental values within some error limit. The resonant eigen frequency agrees
well with that of the internal rf source of ion beam-plasma model origin.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 32-41
Evaluation of partial and total structure factors, Bhatia-Thornton
correlation functions, compressibility and diffusion coefficient of
Pb-Pd alloy at different compositions and temperatures
Sumita Bandyopadhyay, R Venkatesh & R V Gopala Rao
The partial and total structure factors of Pd-Pb alloy have been computed using Lebowitz solution of hard spheres with
a square well attractive tail. The calculated values of the total structure factors and also that of the reduced radial
distribution function are in excellent agreement with experiment. It is found that the partial structure factors show
peculiarities due to the formation of a compound Pb 2Pd as reported by Christian et al.[J Noncryst Solids, 156(1993)38].
Bhatia-Thornton correlation functions are also calculated, namely, SNN(k), which show strong correlation in k-space while
SCC(k) and SNC(k) do not show such correlation. The partial and total radial distribution functions (RDF) are also calculated
from which first coordination numbers are obtained. The RDFs show for all compositions the first peaks at 3.35 Å. Exactly
the same value has been obtained by Christian et al. This value is in no way nearer to the first nearest neighbour distances
in pure Pb or Pd. Thus, the small value of 3.35 Å, which corresponds to the first peak position, has been attributed to the
formation of a compound Pb2Pd, which in crystalline form shows exactly the same distance between unlike neighbouring
atoms. The values of compressibility have also been calculated, which show a bigger value of 41.6  10-12 cm2/dyne at 60
atomic percent of Pb. This also indicates the formation of a compound. The diffusion coefficients have been calculated
through Helfand’s prescription. No observable sudden changes are seen in the case of diffusion coefficient. As suggested by
Christian et al., the authors also calculated the total sum of the partial structure factor Ss(k), namely that of SPb-Pb(k) and
SPb-Pd(k) and a strong right hand shoulder at 60 atomic percent of Pb has been found and this perhaps is a characteristic of
compound formation and the shoulder is obtained at 2.8 Å while in Pb 2Pd an exact distance is found in its crystalline form
between unlike atoms. It may be pointed out Pd-Pb distance in amorphous Pb2Pd compound is exactly 2.83 Å while the
present shoulder is obtained at 2.8 Å. Hence it is concluded that Lebowitz solution with a square well attractive tail
reproduced several characteristics shown in the experiment and also clearly indicate the formation of a compound.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 42-45
Applicability of Van't Hoff equation in calculation of impurities in
liquid crystalline materials
Ravindra Dhar & R S Pandey
Van't Hoff equation has been applied to the binary mixtures of cholesteryl pelargonate (ChP) with nonyloxybenzoic acid
(NOBA) and of cholesteryl myristate (ChM) with dodecyloxybenzoic acid (DDOBA) for different mole concentrations of pure
components. The calculated and added impurities have been compared. The applicability of the Van't Hoff equation depends
upon the degree of miscibility of impurity with the pure component. This equation has also been applied to calculate the
radiation-induced impurities in ChP and ChM.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 46-53
Studies of Mn0.5Cr0.5Fe2O4 ferrite by neutron diffraction at different
temperatures in the range 768K  T  13K
A K M Zakaria, M A Asgar, F U Ahmed, A K Azad, S M Yunus, S K Paranjpe & A Das
Neutron diffraction studies of a polycrystalline manganese-chromium-ferrite with composition Mn0.5Cr0.5Fe2O4 have
been performed at a number of temperatures in the range 768K  T  13K. The cation distributions, oxygen position
parameter (u) and lattice constant (ao) have been determined from the analysis of the higher angle neutron diffraction data.
The temperature response of the lattice constant has also been investigated and a slight anomalous expansion has been
found around the magnetic transition temperature. Sublattice as well as net ferrimagnetic moments of the specimen have
been found out from the analysis of the neutron diffraction data at different temperatures. A randomly canted ordering of
spins has been observed in the B sublattice, while the A sublattice moments appear to exhibit collinear Néel type ordering
at all temperatures
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 54-58
Thermally stimulated conductivity and evaluation of
some parameters of CaS:Pr phosphors
R. N. Dubey, O N Awasthi, V Singh & M Tiwari
Thermally stimulated conductivity (TSC) of CaS:Pr microcrystalline phosphors studied in the temperature range of 300-330 K.
One TSC was observed in the range 311-318 K. Trap depths relaxation times, attempts to escape frequency and initially filled
traps are evaluated using Bucci-Fischi [Bucci C, Fischi R and Guide G, Phys Rev, 148(1956)816] and Cowell-Woods methods
[Cowell T A T and Woods J, Brit J Appl Phys, 18(1967)1045]. An attempt is made to explain initially filled trap density using
Ozawa model [Ozawa L-J, Elec Chem Soc, 120, 140 (1981)] of luminescent center.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 59-61
X-ray analysis of 2-methyl-4-phenyl-3,
4-dihydro-quinazolinium chloride
Rajnikant, V K Gupta, O P Suri & M Lal
The crystal structure of the title compound (C15H14N2.HCl) has been determined by X-ray crystallographic techniques.
The compound crystallizes in the monoclinic space group P21/c with unit cell parameters: a = 9.682(1), b = 10.532(1), c =
13.139(1)Å,  = 90.82(2), Z = 4. The structure has been solved by direct methods and refined to R = 0.057 for 1204
observed reflections and wR(F2) = 0.154. The dihedral angle between the planes of phenyl ring C and the quinazoline
moiety is 79.3(1). The Cl- anion is located 3.109(4) Å from the N3 atom.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 62-68
Micro-crystallographic and spectral response studies of CdSe1-xTex
alloyed thin films
P D More, G S Shahane, L P Deshmukh, P N Bhosale, A A Belhekar & M K Dongare
Chemical deposition of CdSe1-xTex solid solution thin films from salt solutions of cadmium, selenium and tellurium
derivatives of sodium sulphite at 70 C temperature has been presented. The quantitative analyses (EDS and spectrophotometric) showed that the film deposits are Cd rich and compared to the Te, Se content is larger. The variation of xfilm
with xbath is non-linear. The XRD studies show composites to be crystalline in nature and both CdSe and CdTe existed in
both hexgonal wurtzite and cubic zinc blende structures whereas CdSe1-xTex alloys were hexgonal dominating. Both
wurtzite (0  x  0.08) and zinc blende (0  x  0.15) phases undergo solid solution and variation in lattice parameters
followed Vegard’s law. The surface topography showed diffused grain polycrystalline texture with an overgrowth
developed in some cases. The spectral studies of these films gave a continuous change in the optical gap (Eg = 1.76 to 1.45
eV ) with a band to band direct type of transitions.
Indian Journal of Pure & Applied Physics
Vol. 40, January 2002, pp. 69-71
Dielectric relaxation of some rigid polar molecules
and their binary mixture in benzene solution
A D Vyas & V A Rana
Dielectric absorption of rigid polar molecule pyridine and its mixture with benzonitrile in benzene solution has been
studied at microwave frequency 9.1 GHz and at different temperatures (20-47ºC). The relaxation time (0) and distribution
parameter () were evaluated using Higasi’s single frequency method. The thermodynamical parameters were calculated
using Eyring’s rate equations. From the dielectric relaxation and activation energies it is found that the molecules retain
their characteristic behaviour in the mixture.