Rakesh Dogra

In this paper, an impulsive differential system is investigated for the first time for several stability criteria relative to initial time difference. The investigations are carried out by perturbing Lyapunov functions and by using comparison results. A generalized Lyapunov function has been used for the investigation.The results that are obtained...

In this paper, an impulsive differential system is investigated for the first time for practical stability and boundedness criteria with respect to initial time difference. The investigations are carried out by perturbing Lyapunov functions and by using comparison results. A generalized Lyapunov function has been used for the investigation. The pre...

LiF: 0.05 mol%Sm³⁺, 0.08 mol% Dy³⁺with varying concentrations of Eu³⁺(x = 0.02, 0.04, 0.06, 0.08 mol %) nanophosphors were synthesized by chemical co-precipitation method at fixed 8 pH value, to study the thermoluminescence behaviour for dosimetric applications. XRD confirmed the cubical crystalline phase of the nanophosphors. The average size of t...

Present work focused on synthesis of green hydrogel polymer of gum rosin alcohol/psyllium crosslinked poly (acrylic acid) [(GrA-Psy)-cl-PAA] under vacuum condition. Use of both psyllium and gum rosin alcohols as backbones could lessen the burden on the environment, as more natural aspect is drawn in the hydrogel polymer. The various reaction parame...

In this paper, an impulsive differential system is investigated to obtain sufficient conditions for strict practical stability. The investigations are carried out by perturbing Lyapunov function and by using the comparison principle. The stability properties are investigated in terms of two measures. Our results demonstrate that impulses do contrib...

Present study explored the swelling behavior, biodegradability and flocculation efficiency of hydrogel polymer based on renewable backbones‐psyllium and gum rosin. Swelling studies revealed that the polymer sample exhibit pH and temperature‐dependent swelling behavior. The polymer sample was assessed for its flocculation efficiency by optimizing th...

Nanocrystalline powders of lithium fluoride (LiF) doped with samarium (III) (Sm3+) and dysprosium (Dy3+) ions (LiF:Sm3+,Dy3+) have been synthesized through the chemical coprecipitation method at a pH value of 8. The phase purity of the as-grown samples has been confirmed by X-ray diffraction, and the average crystallite size was 32 nm, while transm...

AC transport properties and dielectric response of sandwich geometry (Ag/CuPc/Ag) of CuPc(CuPc) thin films deposited using thermal evaporation technique have been studied within frequency range 1 Hz–10 KHz and in temperature range 303–383 K. Scanning electron microscope (SEM) investigations of these films reveal fiber like morphology. Crystalline n...

The present paper reports the synthesis, characterization and gamma dose induced thermoluminescence properties of LiF: Yb³⁺ nanophosphors. The material was synthesized by chemical co-precipitation method at 8pH value. The crystalline structure and phase purity of the nanophosphors was confirmed by X-ray powder diffraction with an average crystallit...

In the present study, the synthesis of novel semi‐interpenetrating network (Semi‐IPN) hydrogel based on gum rosin alcohol‐psyllium (GrA‐Psy) has been reported. (Gum rosin alcohol‐psyllium)‐crosslinked‐poly(acrylic acid) [termed as (GrA‐Psy)‐cl‐poly (AA)] was synthesized using potassium persulphate (KPS) as an initiator and N, N′−methylene‐bis‐acryl...

In the present paper, a perturbed impulsive differential system is investigated for uniform practical stability. For the same, sufficient conditions have been obtained in terms of two measures by using Lyapunov-like function. An example has also been given to illustrate the derived results.

In the present paper, an impulsive differential system is investigated for uniform eventual practical stability. Sufficient criteria have been obtained for the uniform eventual practical stability of the impulsive differential system in terms of two measures by using Lyapunov-like function. The results that are obtained to investigate the stability...

This paper reports the thermoluminescence (TL) and the kinetic parameters studies of Sm³⁺ doped lithium fluoride (LiF) nanophosphor prepared by chemical co-precipitation method. For the phase purity of the prepared phosphor, X-ray diffraction method has been used and the average crystallite size calculated from XRD peaks using Debye-Scherer’s formu...

A cost-effective drop-cast technique has been used to deposit copper phthalocyanine (CuPc) films on a glass substrate. The obtained films have undergone structural, optical and electrical characterization after annealing at different temperatures-that is, 100, 150 and 200°C. The X-ray diffraction spectra confirm the formation of CuPc films. The abs...

Thermoluminescence (TL) properties of LiF: Sm³⁺ (0.05 mol%) co-doped with Eu³⁺ (0.02, 0.04, 0.06, 0.08 mol%) nanophosphor for the applications of TL dosimetry have been studied. The nanophosphors have been synthesized by chemical co-precipitation method at 8 pH value. The phase purity of the prepared samples has been confirmed by using X-ray diffra...

The present paper reports the structural, optical and electrical properties of zinc phthalocyanine (ZnPc) thin films which were grown by the thermal evaporation technique at different substrate temperatures of 312, 363 and 413 K and dielectric response of sandwich geometry of ZnPc thin films have also been studied within frequency range 1 Hz–50 KHz...

We synthesized single phase pure and Eu doped LiF having micro-cubical morphology by modified co-precipitation method. The complete solid solubility of Eu in LiF has been observed up to 0.04 mol% and afterwards phase segregation started. The absorption spectra of pure and Eu doped LiF revealed the formation of -irradiation induced and dose depende...

Nanocrystalline lithium fluoride (LiF) phosphors have been prepared by the chemical co-precipitation method at different pH values (7.0, 8.0, 9.0 and 10.00). The formation of nanocrystalline structure has been confirmed by X-ray diffraction and transmission electron microscope. Thermoluminescence (TL) properties of LiF phosphors irradiated with...

The perturbed angular correlation technique is very well suited to characterize the structural, dynamic and electronic properties of impurity or impurity-defect complexes on an atomic scale. Using radioisotope probe 100Pd/100Rh, such measurements have been performed to study the palladium related defects in silicon as a function of dopant concentra...

Nanocrystalline lithium fluoride phosphors have been prepared by the chemical co-precipitation method at different pH values (7.0, 8.0 and 9.0). The formation of nanocrystalline structure has been confirmed by X-ray diffraction and transmission electron microscope. The thermolumniscence properties of lithium fluoride phosphors irradiated with gamma...

Nanocrystalline lithium fluoride phosphors have been prepared by the chemical co-precipitation method at dif-ferent pH values (7.0, 8.0 and 9.0). The formation of nanocrystalline structure has been confirmed by X-ray diffraction and transmission electron microscope. The thermolumniscence properties of lithium fluoride phos-phors irradiated with gam...

The local structural and electronic environment around ¹¹¹Cd guest atoms in pure and transition metal doped Zn_1-xTM_xO nanocrystalline powders (TM = Co, Mn, Cu and x = 0.01, 0.02, 0.05) was monitored on an atomic scale, by perturbed angular correlation (PAC) spectroscopy, with high precision. For these measurements,...

Local structural and electronic environment around 111In probe atoms in transition metal doped Zn1 − xTxO (T=Mn, Co, V and Ni; x = 0.01, 0.02, 0.05) and Cu co-doped Zn1 − xCoxCu0.01O (x = 0.01–0.04) have been monitored on an atomic scale by Perturbed Angular Correlation (PAC) spectroscopy. Single phase nanocrystalline powders were synthesized at lo...

In this work, a direct precipitation method using wet chemical reaction was used to synthesize pure and doped ZnO nanoparticles. The zinc nitrate and sodium hydroxide were used as staring materials to precipitate the desired nanoparticles followed by calcinations at temperatures of 500-700 o C. The phase purity and crystallite size of as grown part...

The structural and electronic environment about implanted radioactive (111)In(->(111)Cd) probe atoms as a function of annealing temperature in a single crystal of ZnO(0001) has been monitored on an atomic scale using perturbed angular correlation technique, a nuclear hyperfine method. This technique is based upon the hyperfine interaction of the nu...

Several experimental techniques are available to investigate materials but microscopic techniques based on hyperfine interaction form a subclass that can characterize materials at the smallest possible atomic scale. The interaction of the nuclear electromagnetic moments with the hyperfine fields arising from the extranuclear electronic charges and...

The magnetic hyperfine fields of Cd guest atoms in nickel have been measured by perturbed angular correlation spectroscopy with an unprecedented precision. The experiments exhibit the well-known oscillations which have been attributed to the substitutional and the cubic C-site of Cd in nickel, but also show the existence of previously unknown sites...

The perturbed angular correlation technique has been utilized to understand the production and nature of the implantation induced crystalline to amorphous transformation in GaAs and InAs. This technique, which is based upon the nuclear hyperfine interaction of the electric-quadrupole moment of the probe nucleus with the electric field gradient from...

Using 100Pd/100Rh probes, perturbed angular correlation measurements were performed to study Pd-related defects in Si as a function of dopant concentration and dopant type. Pd-vacancy and Pd-B complexes were identified by their characteristic electric field gradients in highly doped n- and p-type Si, respectively. Both pairs exhibited a T3/2 temper...

The recovery of crystallinity as a function of annealing temperature in GaP recoil-implanted with 111In has been monitored on an atomic scale using the perturbed angular correlation (PAC) technique. This technique is based on hyperfine interaction of the electric quadrupole moment of probe nuclei with the electric field gradient (EFG) of the host l...

The structural relaxation of irradiated III–V compound semiconductors InP, GaAs and InAs arising from room temperature anneal-ing has been studied using perturbed angular correlation spectroscopy. Amorphous zones were produced by MeV Ge ion implantation in single crystal substrates at liquid nitrogen temperature. These amorphous zones were found to...

Strain in Si induced by ion irradiation at temperatures of 200–400 °C has been measured at room temperature. Quantitative analysis of the strain distribution produced by 750-keV Si ion implantation in Si substrates was characterized by double-crystal X-ray diffraction (DCXRD). Strain in the Si surface layer was determined by modeling the DCXRD rock...

The local structure and stability of an impurity complex of palladium in silicon has been studied on an atomic scale by perturbed angular correlation spectroscopy using the 100 Pd/Rh probe nuclei. Palladium exists as an acceptor Pd À in n-type silicon and donor Pd þ=2þ in p-type silicon. Owing to the Coulomb attraction between oppositely charged im...

Elastic recoil detection with swift heavy ion projectiles enables the direct and calibration-independent quantification of the N/In ratio and the impurity content of indium nitride thin films. The beam-induced dissociation of In and N can either be avoided or correctly be modelled, so that precise atomic fractions for In, N, O, C, and H can be dete...

A Pd-vacancy Pd-V − complex in Si has been identified with the perturbed angular correlation technique using the radioactive 100 Pd probe produced by recoil implantation. The fraction of Pd probes in the complex has been determined as a function of dopant type B, P, As, and Sb, dopant concentration 10 15 –6 10 19 cm −3 and annealing temperature 21–...

The time differential perturbed angular correlation (TDPAC) technique was used to study the temperature dependence of electric field gradient (EFG) in LaCoO3 perovskite using and nuclear probes. The radioactive parent nuclei 111In and 181Hf were introduced into the oxide lattice through a chemical process during sample preparation and were found to...

The crystal lattice of bulk grains and state-of-the-art films of indium nitride was investigated at the atomic scale with perturbed angular correlation spectroscopy using the 111In/Cd radioisotope probe. The probe was introduced during sample synthesis, by diffusion and by ion implantation. The mean quadrupole interaction frequency νQ = 28 MHz was...

The Perturbed Angular Correlation (PAC) technique was used to study the quadrupole interactions in the La1−x SrxCoO3 (0 ≤ x ≤ 0.08) perovskites using 111Cd and 181Ta probes. The radioactive parent nuclei 111In and 181Hf were introduced in the oxide lattice through chemical process during sample preparation and found to occupy only Co sites. The mea...

A radioisotope ion implanter has been developed using a cesium-sputtering, negative ion source, which offers versatility and sustained operation. Employing the molecular 111In16O− ion, μCi activities of the radioisotope probe 111In/Cd have been implanted into different material hosts. The implanted tracer activity has been shown to be sufficient fo...

TDPAC has been employed to study the local structure of implanted palladium in silicon utilizing 87-75 keV γ-γ cascade of probe nucleus 100Pd. The observed hyperfine parameters revealed the presence of Pd-V defect pair only in highly doped n-type silicon. A dumbbell structure with substitutional palladium and silicon vacancy as nearest neigbor is s...

The lattice structure of both InN grains with submicron dimensions and a MBE-grown InN film have been studied with the radioisotope probe 111in/Cd and Perturbed Angular Correlation spectroscopy. The quadrupole interaction frequency of the probe in this material has been measured to be of the order of 28 MHz, consistent with results for ALN and GaN....

The Perturbed Angular Correlation (PAC) technique was used to study the quadrupole interactions in the La 1 j x Sr x CoO 3 (0 e x e 0.08) perovskites using 111 Cd and 181 Ta probes. The radioactive parent nuclei 111 In and 181 Hf were introduced in the oxide lattice through chemical process during sample preparation and found to occupy only Co site...

A radioisotope ion implanter has been developed using a cesium-sputtering, negative ion source, which offers versatility and sustained operation. Employing the molecular 111 In 16 O j ion, mCi activities of the radioisotope probe 111 In/Cd have been implanted into different material hosts. The implanted tracer activity has been shown to be sufficie...

TDPAC has been employed to study the local structure of implanted palladium in silicon utilizing 87–75keV γ–γ cascade of probe nucleus 100Pd. The observed hyperfine parameters revealed the presence of Pd–V defect pair only in highly doped n-type silicon. A dumbbell structure with substitutional palladium and silicon vacancy as nearest neigbor is su...

Among the several experimental techniques based on different principles available to investigate the materials, the microscopic techniques based on hyperfine interaction form a subclass that characterizes a material at the smallest possible atomic scale. After an introduction to the basic properties of the transition metal perovskites of type ABO3,...

The time differential perturbed angular correlation (TDPAC) technique has been used to study the nuclear quadrupole interactions of the first excited state of ground state rotational band (2+, 80 keV, T1/2 = 1.88 ns) and the band head of the K = 41- band (4-, 1094 keV, T1/2 = 120 ns) in the 168Er nucleus of a polycrystalline Er host. At room temper...

Time Differential Perturbed γ–γ Angular Correlation (TDPAC) technique was used to measure the magnetic hyperfine field at both Ge and Ce sites in CeMn2Ge2 and CeCo2Ge2 intermetallic compounds. The 111In (111Cd) probe nuclei was used to investigate the hyperfine interaction at Ge sites, while the 140La (140Ce) nuclei was used to measure the magnetic...

The perturbed angular correlation (PAC) technique has been used to study the electric field gradient (EFG) in LaCoO3 perovskite. The results are compared with those for LaCrO3, LaFeO3 measured earlier. The PAC probe, 111In → 111Cd, was introduced in the oxide lattice by means of chemical reaction during sample preparation. In the present work, the...

The electric field gradient at transition element impurities 99Ru and 100Rh in metallic rare earth hosts Pr, Nd and Tb has been investigated by time differential perturbed angular correlation (TDPAC) technique at room temperature. The electric field gradients, calculated from the measured quadrupole interaction frequencies at room temperature, are;...

The perturbed angular correlation (PAC) technique was used to study the hyperfine interactions in the antiferromagnetic and paramagnetic regions of the distorted perovskites LaCrO3 and LaFeO3. The dilute 111In-->111Cd nuclear probes were introduced into the samples through a chemical process. The present measurements cover the temperature ranges fr...

Time differential perturbed angular correlation measurements were carried out using short lived isomeric 5/2+ state in 147Pm to investigate the magnetic and electric hyperfine interactions in Nd and Gd hosts at different temperatures. At 10 K the magnetic hyperfine fields at 147Pm in Nd and Gd hosts are 361(42) kG and 256(30) kG, respectively, and...

The electric quadrupole moments of the 9/2− and 21/2− isomeric states of 173Ta at 165.8 keV and 1713.2 keV, respectively, were measured as Q(9/2−)=2.92(15) b and Q(21/2−)=6.23(18) b for the first time using the TDPAD technique. A 66 MeV pulsed 12C ion beam from the 15UD pelletron accelerator facility of the Nuclear Science Centre at New Delhi was u...

Systematic DPAC measurements of the electric field gradient at Dy in very low concentration in pure Pr, Nd, Gd, Tb, Dy, Ho and Er metals in the paramagnetic phase have shown for the first time the host associated aspherical 4f-shell effects. The results are compared with the presently available first-principles based calculations of the electric fi...

The electric quadrupole moment of the 9/2− isomer in the171Ta nucleus, populated in the159Tb(16O,4nγ)171 Ta reaction, has been measured for the first time using the TDPAD technique. The measured value Q(9/2−)=3.09(19) b andB(M1)/B(E2) ratios, deduced from the existing γ-ray spectroscopic data, have been used to derive shape parameters for the πh11/...