Total visitors: 1,718  since 4-05-05

Indian Journal of Pure and Applied Physics

 

 

 

 ISSN: 0019-5596

CODEN: IJOPAU 43 (4) 233 - 314

Volume 43

Number 4

April 2005

  

 

CONTENTS

 

Atomic and Molecular Physics

 

Spectroscopic studies of molecules observed in comets

R R Reddy*, K Rama Gopal, Y Nazeer Ahammed, D Baba Basha,K Narasimhulu & L Siva Sankar Reddy

237

   

Spectral lines of some volatile hydride forming elements for determination of excitation temperature in analytical plasmas

M A Eid*, H R Moustafa, E A Al-Ashkar & S S Ali

246

   
Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics

 

All-optical system for wide range decimal multiplexing

Archan Kumar Das & Sourangshu Mukhopadhyay*

253

   

Ultrasonic studies on dilute solutions of water in n-alcohols and 2-alkoxyethanols

G Venkata Ramana, E Rajagopal & N Manohara Murthy*

259

Condensed Matter: Structural, Mechanical and Thermal Properties

 

Extending Wertheim’s perturbation theory to aperiodic solids

Pavan Kumar Verma, D K Dwivedi & K N Khanna*

265

Absolute thermo-electric power in heavily doped n-type silicon

Bantikassegn Workalemahu

270

Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties

 

Magnetic order and  electrical resistance in manganites

R J Singh* & P K Sharma

273

Study of PrxY1-xBa2Cu3O7-d  high Tc superconductors

B N Dole* & S S Shah

279

   

Dielectric study of surface modification of linear low density polyethylene treated with chromic acid and sodium carbonate

S K Dash, K C Mishra, S N Mishra & B B Swain*

287

   

Effect of processing and polarizer on the electrical properties of Mn-Zn ferrites

Madan Lal*, D K Sharma & M Singh

291

   

Study of N M R spin lattice relaxation of several aldehydes

S K Vaish, Anupam Singh, A K Singh & N K Mehrotra*

295

Interdisciplinary Physics and Related Areas of Science and Technology

 

Novel power VDMOSFET structure with vertical floating islands and trench gate

Rakesh Vaid* & Naresh Padha

301

   

Point contact one injection current in solid insulators with traps

N K Sharma* & P M Anbarasan

308

 

________

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.


 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 237-245

 

Spectroscopic studies of molecules observed in comets

 R R Reddy, K Rama Gopal, Y Nazeer Ahammed, D Baba Basha, K Narasimhulu & L Siva Sankar Reddy

 

The potential energy curves for the different electronic states of molecules like N2+, N2, OH and S2 observed in comets are constructed by using the Rydberg–Klein–Rees method as modified by Vanderslice et al. The ground state dissociation energies are determined by curve fitting technique using the five parameter Hulburt-Hirschfelder (H-H) function. The estimated dissociation energies are 8.587±0.248, 9.620±0.275, 4.308±0.118 and 4.325 ±0.115 eV for N2+, N2, OH and S2 respectively. These values are in good agreement with the literature values. The r-centroids and Franck-Condon factors (FC factors) for the band system of A–X system of N2+ and A–X and B–X system of N2 molecules have been calculated employing approximate analytical methods of Jarmain and Fraser and Nicholls and Jarmain. The absence of the bands in these systems is explained.

Keywords: Comets, Franck-Condon factors, r-centroids, Astronomical spectra, Potential energy curves

 

IPC Code: G01J3/28

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp 246-252

 

Spectral lines of some volatile hydride forming elements for determination of excitation temperature in analytical plasmas

M A Eid, H R Moustafa, E A Al-Ashkar & S S Ali

 

The spectra of some volatile hydride forming elements have been investigated to select thermometric species for determination of excitation temperature in analytical plasmas working in argon under atmospheric pressure. Groups of lines of As I, Sb I and Sn I in addition to Ar I were found appropriate for the determination of excitation temperature in inductively coupled plasma (ICP) and wall-stabilized arc (WSA). The Boltzmann plots were straight lines, which determined temperature in ICP and WSA using different groups of spectral lines that agree well with each other as well with the most familiarly used thermometric species. These lines are recommended for determination of temperature when gaseous hydrides are introduced into the plasma and no other thermometric species except the atoms of working gas are present.

 

Keywords: Excitation temperature, Inductively coupled plasma, Wall-stabilized arc, Volatile hydride forming elements

 

IPC Code: H03L7/26

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 253-258

 

   All-optical system for wide range decimal multiplexing

 Archan Kumar Das & Sourangshu Mukhopadhyay

 

In all-optical parallel information processing, data computation and in optical communication, multiplexing and de-multiplexing have a very strong role. Many multiplexing schemes in digital optical processing are already proposed. A new type of all-optical digital multiplexing system with only two triggering channels has been reported. Any input channel can be multiplexed here out of any number of such input channels with only those two triggering channels.

Keywords: Optical computation, Spatial input encoding, Parallel processing, Logic operations, Multiplexing

 

IPC Code: G02F3/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 259-264

 

Ultrasonic studies on dilute solutions of water in n-alcohols and 2-alkoxyethanols

G Venkata Ramana and E Rajagopal & N Manohara Murthy

 

Ultrasonic velocities in dilute solutions of water in n-alcohols (methanol, ethanol, n-propanol and n-butanol), and
2-alkoxyethanols (2-methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol) have been determined at 298.15 K using single crystal variable path interferometer working at 3 MHz. The excess ultrasonic velocities have been evaluated using the formula, which is thermodynamically valid. A distinctive non-linear variation of ultrasonic velocity with concentration of water in both n-alcohols and 2-alkoxyethanols has been observed over a small range of concentration. A similar behaviour is also observed in the concentration dependence of excess ultrasonic velocity in these solutions. This behaviour has been explained by considering the existence of water molecules as monomers up to certain optimum concentration, (X2)opt, of water and the non-linear behaviour observed beyond (X2)opt has been explained in the light of water-water and water-alcohol interactions leading to the formation of islands of water-alcohol extended structures.

 

Keywords: Ultrasonic study, Water, n-alcohols, 2-alkoxyethanols

 

IPC Code: B01J19/10

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 265-269

   

Extending Wertheim’s perturbation theory to aperiodic solids

 Pavan Kumar Verma, D K Dwivedi & K N Khanna

 

A theoretical study of two-dimensional hard homonuclear dumbbell-shaped aperiodic molecular system with a high anisotropy parameter d* = 0.924 employing Wertheim’s first-order perturbation theory has been reported. The thermodynamic state of the aperiodic molecular solid known as DC-crystalline phase has been presented. The equation of state of two-dimensional dumbbell shaped molecules in fluid, HB and DC crystalline phases has been compared.

Keywords : Wertheim’s Perturbation theory, Aperiodic Solids, Anisotropy parameter

 

IPC Code: G01K

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 270-272

  

Absolute thermo-electric power in heavily doped n-type silicon

 Bantikassegn Workalemahu

 

The absolute thermoelectric power in a heavily doped n-type silicon by taking into account the effect of band tails has been calculated. The calculations show that the effect of incorporating the band tails results in increasing the value of absolute thermoelectric power.

Keywords: Thermoelectric power, n-type, Silicon, Band tails

 

IPC Code: H01L

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 273-278

 

Magnetic order and electrical resistance in manganites

 R J Singh & P K Sharma

 

The electrical resistance versus temperature behaviour of the manganites La1-xBaxMnO3 (x=0.3,0.4,0.5); La1-xPbxMnO3 (x = 0.2,0.3,0.33) and La1-xSrxMnO3 (x = 0.1,0.2,0.4) has been investigated. The temperatures at which the substances have maximum resistance have been found to be much lower than their Curie temperatures. The variation of resistance with temperature is not smooth, but the graphs show different slopes. The electron paramagnetic resonance of these substances shows a new signal in the spectra on a little increase of microwave field from the usual values. It has been interpreted as phase separations in the materials with Mn3+ and Mn4+ spins aligned in opposite directions. Based on this idea, magnetic order and electrical resistance of the materials are shown to be directly correlated.

Keywords: Manganites, Electron paramagnetic resonance, Phase separations

 

IPC Code : G01R27/02; H01F1/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp 279-286

 

 Study of PrxY1-xBa2Cu3O7-d high Tc superconductors

B N Dole & S S Shah

 

The substitution of Pr in high Tc superconducting compound plays very interesting role such as annihilation of superconductivity with increase of Pr concentration, which is not adequately explained yet. The samples of the system
Y1-xPrxBa2Cu3O7-d with compositions (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by well known conventional ceramic route and chemical route. The results of resistivity, X-ray diffraction, orthorhombicity, X-ray density, bulk density, volume cell and oxygen content of both the routes are reported. The samples prepared by chemical route give better results than conventional ceramic route. Bond distances obtained from neutron diffraction show that the electron phonon interaction becomes weaker and results in loss of superconductivity.

 

Keywords: Superconductor, X-ray diffraction, Orthorhombicity, Neutron diffraction, Electron-phonon interaction

 

IPC Code: H01L39/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 287-290

  

Dielectric study of surface modification of linear low density polyethylene treated with chromic acid and sodium carbonate

 S K Dash, K C Mishra, S N Mishra & B B Swain

 

Received 12 February 2004; revised 3 November 2004; accepted 25 January 2005

The relative permittivity (e˘) and dielectric loss (e˘˘) of linear low density polyethylene (LLDPE) sample of 60 μm thickness treated successively with a highly oxidizing environment like chromic acid of normality N/5 to N/30 for time duration of 0.5 to 12 hr and sodium carbonate for 24 hr are measured using GRA 650A impedance bridge over 100 Hz to 10 kHz range at 303.16±1K. The N/10 chromic acid treated sample exhibited increase in values of e˘ (from 3.2 to 4.3) and e˘˘ (from 0.48 to 0.75) relative to the virgin sample at 300 Hz while the rest of the samples recorded reduction. But these chromic acid treated LLDPE samples being further treated with N/10 sodium carbonate (Na2CO3), exhibit change in e˘ and e˘˘ values in as much as those for N/10 chromic acid treated sample drops while that of N/15 chromic acid treated sample increases significantly. This indicates intense polarization penetrating to reasonable depth of the surface of the material. The higher value of e˘ and e˘˘ in N/10 chromic acid treated sample may be due to intra-molecular three-dimensional network of H-bonding between PE-COOH species. Attempt is made to explain these features.

Keywords: Relative permittivity, Dielectric loss, Linear low density polyethylene, Polymers

 

IPC Code: G01R31/12

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 291-294

 

  Effect of processing and polarizer on the electrical properties of Mn-Zn ferrites

 Madan Lal, D K Sharma & M Singh

 

The effect of processing technique as well as the effect of oxidizing agent on the electrical properties of Mn0.47Zn0.53Fe2O4 ferrite has been presented. The dc resistivity is improved by citrate precursor method as compared to normal ceramic method and it is further improved by the addition of H2O2 (hydrogen peroxide), which acts as a strong oxidizing agent. The decrease in dielectric constant and dielectric loss factor by addition of oxidizing agent is justified by inverse proportionality between resistivity and dielectric constant.

Keywords: Mn-Zn, Ferrites, Oxidizing agent, Electrical properties

 

IPC Code: G01R27/26, B23H1/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp 295-300

 

Study of NMR spin lattice relaxation of several aldehydes

S K Vaish, Anupam Singh, A K Singh & N K Mehrotra

 

The NMR spin lattice relaxation of various aldehydes has been investigated. The experimental values of NMR spin lattice relaxation time T1 of benzaldehyde, anisaldehyde, o-cholorobenzaldehyde and p-hydroxybenzaldehyde have been correlated with the calculated value of N M R spin lattice relaxation time T1 obtained using various equations for dielectric relaxation time t. It has been concluded that Writz equation and Murty equation are better substitute for the correlation time in calculating NMR spin lattice relaxation time than Debye equation as used by BPP (Bloembergen, Purcell and Pound).

 

Keywords: NMR spin lattice relaxation, Aldehydes

 

IPC Code: G01R33/20

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 301-307

  

Novel power VDMOSFET structure with vertical floating islands and trench gate

 Rakesh Vaid & Naresh Padha

 

A novel power VDMOSFET (vertical double-diffused MOSFET) structure, simulated using PISCES-II, a 2-dimensional numerical device simulator has been described. The proposed device structure is based on the floating islands (FLI)-diode concept and trench gate technology. Extensive simulations were performed to understand physics of the device through various internal electrical quantities like potential distribution, electric field, etc. in different regions of the device both in on/off states.The simulation results show that the new device has a low on-resistance by virtue of reduced electric field in its drift region as well as due to the removal of parasitic JFET region resistance. Trench gate acts as a field plate to avoid the punch-through thus enhancing the breakdown voltage. For a 100 Volts design, an approximate 15% increase in the breakdown voltage has been observed in the proposed device compared to the conventional FLIMOSFET without trench gate.

 

Keywords: Power MOSFET, VDMOSFET, FLIMOSFET, Device simulation

 

IPC Code: H01J 1/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, April 2005, pp. 308-310

 

  

Note

 

  Point contact one injection current in solid insulators with traps

 N K Sharma & P M Anbarasan٭

 

One injection current in insulator has been studied widely for a long time in various geometries. An important field for study is the analytical treatment of current carriers in deep trap region well below the fermi level. In the present problem, a cylindrical structure has been taken into consideration. The effects of traps are included in the analysis. The problem becomes complicated in the presence of traps and thermal free carriers because there are various transitions regimes present in the complete current-voltage characteristics.

 

Keywords: Point contact, Injection current, Traps, Insulators

 

IPC Code: H01B