Nampoori, V P N; Kamalasanan, M N; Patel, M M(IOP, 1975)
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Abstract:
Indium monofluoride was excited in a high-frequency discharge and the C-X system was photographed at a reciprocal dispersion of 0.3 AA mm-1 using a plane-grating spectrograph. Rotational analyses of the 0,0 1,0 2,2 3,3 4,4 2,4 3,5 4,6 and 5,7 bands have been carried out and the following molecular constants have been evaluated. Be'=0.2670(+or-3) cm-1, Be"=0.2628(+or-4) cm-1, alpha e'=0.0050(+or-4) cm-1, alpha e"=0.0020(+or-1) cm-1, De'=3.65(+or-5)*10-7 cm-1, De"=2.5(+or-3)*10-7 cm-1, beta e'=0.5(+or-2)*10-7 cm-1, beta e"=0.2(+or-1)*10-7 cm-1, re'=1.9672(+or-3) AA, re"=1.9853(+or-2) AA. The re" value agrees with the microwave absorption value 1.9854 AA.
Lalitha, P R; Rao, V R; Nampoori, V P N(Current Science, 1980)
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Abstract:
Excitation and emission spectra of SrS : Mn : Ce phosphors have been studied in detail
at various Mn and Ce concentrations. In order to study the effect of external pressure on phosphors,
the samples were pretreated under various pressures. Four bands around 470 nm, 530 nm,
310 nm and 620 nm were observed, when the samples were excited with 265 nm radiation. The
effect of pressure is to reduce the fluorescence ability of the phosphors, and the luminescence
vanishes above O· 1 ton m-2 pressure. The fluorescence ability, however, can be regained on retiring
the sample. The emission mechanism has been attributed to two luminescentcenters in the forbidden
gap. An appreciable amount of photocurrent has also been observed for the sample.
Sudha Kartha, C; Ramachandran, T; Nampoori, V P N; Sathianandan, K(Solid State Communications, 1986)
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Abstract:
Variations in the decay times of the characteristic green emissions at 522.7, 551.3, 549.6, 547.6, 542.2, 540.2, 535.9 and 533.5nm from
CaF2 :H03+ with concentration are studied at RT and LNT. A pulsed N2
laser beam of power density 1.5 MW cm-2 is used for the excitation.
Temperature dependent concentration quenching of the decay times are
observed for all the emission bands. But an increase in the decay time due
to the reabsorption process is also observed for a few of the above bands.
Abdul Rasheed, T M; Nampoori, V P N; Sathianandan, K(Chemical Physics, 1986)
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Abstract:
The vibrational overtone spectra 0f the liquid phase 1,2-dichloroethane and 1,2-dibromoethane in the spectral regions of
CH stretching local mode overtones corresponding to delta v CH= = 2 to delta v CH=5 are reported. The observed spectral features are
assigned using the local mode model. LocaI mode frequencies WCH and diagonal local mode anharmonicities XCH are
obtained from an analysis of the spectra. The local-local combinations observed are interpreted on the basis of a coupled CH
oscillator model hamiltonian. Local-normal combinations show complex structures and their possible assignments are given.
Abdul Rasheed, T M; Moosad, K P B; Nampoori, V P N; Sathianandan, K(American Chemical Society, 1987)
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Abstract:
Vibrational overtone spectra of acetophenone and benzaldehyde in the visible and near-infrared regions are studied by the
dual beam thermal lens and the conventional near-infrared absorption techniques. The observed increase in the mechanical
frequency of the aryl CH bond from that of benzene is attributed to the decrease in the aryl CH bond length caused by
the electron-withdrawing property of the substituents. Overtone spectra also demonstrate that acetophenone contains two
types of methyl CH bonds arising from the anisotropic environments created by oxygen lone pair and carbonyl P electrons.
The local-mode parameters of the two types of CH bonds are compared with those of acetone and acetaldehyde. The possible
factors influencing the methyl CH bonds in acetophenone are discussed.
Lalaja, Varghese; Nampoori, V P N; Pratap, R(Current Science, October 20, 1987)
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Abstract:
A mathematical analysis of an electroencephalogram of a human Brain during an epileptic
seizure shows that the K2 entropy decreases as compared to a clinically normal brain while the
dimension of the attractor does not show significant deviation.
Reghunath, A T; Nampoori, V P N(Springer, November , 1987)
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Abstract:
Using laser transmission, the characteristics of hydrodynamic turbulence is studied following one of the recently developed technique in nonlinear dynamics. The existence of deterministic chaos in turbulence is proved by evaluating two invariants viz. dimension of attractor and Kolmogorov entropy. The behaviour of these invariants indicates that above a certain strength of turbulence the system tends to more ordered states.
Pratap, R; Nampoori, V P N; Lalaja, Varghese(International Journal of Neuroscience, 1988)
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Abstract:
It is shown that the invariant integral, viz., the Kolmogorov second entropy, is eminently suited to characterize EEG quantitatively. The estimation obtained for a "clinically normal" brain is compared with a previous result obtained from the EEG of a person under epileptic seizure.
Ravisankar, M; Reghunath, A T; Sathianandan, K; Nampoori, V P N(Optical Society of America, September 15, 1988)
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Abstract:
The split-pulse laser method is used to reinvestigate the optical attenuation of distilled water in the region from 430 to 630 nm. The studies are then extended to ionic solutions of NaCl, MgCl2, and Na2SO4, these salts forming the major constituents of seawater. The effect of the concentration of these constituents on optical attenuation is investigated. Further, optical attenuation studies are carried out for the region from 430 to 630 nm for an aqueous solution prepared with all the major constituents in the same proportions as in natural seawater. These values are then compared with values obtained for natural seawater. The relative role of dissolved salts and suspended particles on optical attenuation in seawater is discussed. The lowest attenuation is observed at ~450 nm for all solutions and is found to coincide with that for distilled water.
Reethamma, Thomas; Nampoori, V P N(Elsevier, December , 1988)
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Abstract:
Photoluminescence, thermoluminescence and phosphorescence studies of cerium and copper doped BaS phosphors are attempted. Cu+ centres in BaS lattice activate red emission while Ce3+ sensitize the blue emission. Results are explained on the basis of superposition theory involving monomolecular kinetics. In Randall and Wilkins model, the decay and TL studies are found to corelate each other.
Lalaja, V; Nampoori, V P N; Pratap, R(Kluwer Academic Publishers, February , 1989)
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Abstract:
The theory of deterministic chaos is used to study the three rings A, B, and C of Saturn and the French and Cassini divisions in between them. The data set comprises Voyager photopolarimeter measurements. The existence of spatially distributed strange attractors is shown, implying that the system is open, dissipative, nonequilibrium, and non-Markovian in character.
Abdul Rasheed, T M; Moosad, K P B; Nampoori, V P N; Sathianandan, K(Springer, September , 1989)
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Abstract:
Vibrational overtone spectra of styrene (liquid) and polystyrene (solid), studied by the laser-induced thermal lens (for ΔV=6) and the conventional near infrared absorption (for ΔV=3–5) techniques, are reported. For polystyrene, the overtone energy-bond length correlation predicts that the aryl CH bonds are ∼0.0005 Å longer than that in benzene, while no such conclusions could be drawn on styrene. Thesp 3 CH overtones in polystyrene are observed on the low energy side of the aryl CH overtones.
Reethamma, Thomas; Nampoori, V P N(Elsevier, 1990)
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Abstract:
Fluorescence of BaS: Sm phosphor has been studied using a pulsed Nitrogen laser (337.1 nm) as the excitation source. The spectrum consists of a broad band in the region 540–660nm superposed by the characteristic Sm3+ lines. Energy level splitting pattern of Sm3+ due to crystal field effects has been calculated and relevent field parameters are evaluated. Analysis shows that Sm3+ takes up Ba2+ substitutional sites.
Moosad, K P B; Abdul Rasheed, T M; Nampoori, V P N; Sathianandan, K(Optical Society of America, 1990)
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Abstract:
Low power optical phase conjugation in polyvinyl alcohol
films embedded with saturable dyes is reported. Phase
conjugate reflectivity achieved is higher than that obtained
in the case of similar gelatin films.
Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Indian Journal of Physics, 1992)
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Abstract:
A simple fiber optic concentration sensor based on the coupling of light f rom one
fiber to another through a solution is discussed. The operational characteristics of the sensor are
illustrated by taking the solutions of potassium permanganate and fast green dye as samples.The extrinsic type sensor described here shows linearity at lower concentrations.
Thomas, Baby; Nampoori, V P N(Solid State Communications, 1992)
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Abstract:
A method of preparation of strontium sulphide phosphors doped
with europium is given. Nitrogen laser excited fluorescence emission
spectra of these phosphors in the visible region are recorded. A band
with line structure in the region 350-430 nm and a new broad band at
460 nm are observed. The splitting pattern for the 6p levels of Eu 2+ are
given.
Rajasree, K; Ravi Kumar, A V; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Springer, April , 1992)
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Abstract:
Photothermal deflection technique was used for determining the laser damage threshold of polymer samples of teflon (PTFE) and nylon. The experiment was conducted using a Q-switched Nd-YAG laser operating at its fundamental wavelength (1-06μm, pulse width 10 nS FWHM) as irradiation source and a He-Ne laser as the probe beam, along with a position sensitive detector. The damage threshold values determined by photothermal deflection method were in good agreement with those determined by other methods.
Rajasree, K; Vidyalal, V; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(IOP, 1993)
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Abstract:
The phenomenon of mirage effect suffered by a He-Ne laser beam has been utilized to detect phase transitions in solids. It has been observed that anomalous fluctuations of large amplitude occur in the signal level near the transition temperature. The mean square value of the fluctuation is found to exhibit a well-defined peak at this point. Results of measurements made in the case of crystals of TGS ((NH2CH2COOH)3.H2SO4) and a ceramic sample (BaTiO3) are given to illustrate this technique.
Sasi Kumar, P R; Ambadi, B; Nampoori, V P N; Vallabhan, C P G(Springer, February , 1993)
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Abstract:
Doppler limited high resolution spectrum in the wavelength region 17224 to 17236 cm−1 of the first positive system (B 3Π g −A 3Σ u + ) of the N2 molecule is recorded by optogalvanic spectroscopic technique using a single mode ring dye laser. It is observed that the intensity and line width of the rotational line increase with the discharge current. Dependence of the collision broadening coefficient on the current was also evaluated.
Rajasree, K; Vidyalal, V; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(American Institute of Physics, August 1, 1993)
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Abstract:
Laser‐induced damage and ablation thresholds of bulk superconducting samples of Bi2(SrCa)xCu3Oy(x=2, 2.2, 2.6, 2.8, 3) and Bi1.6 (Pb)xSr2Ca2Cu3 Oy (x=0, 0.1, 0.2, 0.3, 0.4) for irradiation with a 1.06 μm beam from a Nd‐YAG laser have been determined as a function of x by the pulsed photothermal deflection technique. The threshold values of power density for ablation as well as damage are found to increase with increasing values of x in both systems while in the Pb‐doped system the threshold values decrease above a specific value of x, coinciding with the point at which the Tc also begins to fall.