Dynamics of I<SUP>&#8727;</SUP>(<SUP>2</SUP>P<SUB>&#189;</SUB>)production in the ultraviolet photodissociation of alkyl iodides

The relative quantum yields, &#934;&#8727;, for the production of I&#8727;(2P&#189;) at 266,280, and -305 nm are reported for a series of primary alkyl iodides using the technique of two-photon laser-induced fluorescence for the detection of I (2P3/2)and I&#8727;(2P&#189;) atoms. Results are analyzed by invoking the impulsive energy disposal model, which summarizes the dynamics of dissociation as a single parameter. Comparison of our data with those calculated by a more sophisticated time-dependent quantum mechanical model is also made. Near the red edge of the alkyl iodideA band, absorption contribution from the 3Q1 sta1te is important and the dynamics near the 3Q o - 1Q1curv e-crossing region seem to be influenced by the kinematics of the dissociation process

Photodissociation dynamics of small molecules: dissociation of alkyl iodides in the near ultraviolet

In this article we have briefly presented various techniques that are employed to study photodissociation dynamics of small molecules in the gas phase, insofar the energy partitioning among the product modes is concerned. Dynamics of dissociation of methyl iodide as well as other related iodides =~260 nm have been treated in detail citing several experimental techniques utilized to obtain nascent energy distribution in the fragments. The influence of excited state potential energy surfaces on the quantum yield of excited iodine atom (2P½) production, or in the release of most of the available energy into the vibrational modes of alkyl fragments have been discussed

Partially oxidized ferrocenyl complexes for nonlinear optics

Second-order nonlinearity (p) in a series of partially oxidized bisferrocenes linked through conducting -C=N- linkages has been measured and found to vary linearly with the redox potential difference between the ferrocene moiety and the oxidant

Bait specificity in Hook and line fishery of River Ganga and associated conservation issues

Recent survey in lower 1,110 km stretch of River Ganga regarding ‘hook and line’ fishery revealed that fishers apply their inherited indigenous knowledge for selection of bait to harvest finfish and shellfish from river water. A total number of 26 different types of baits under 07 categories were recorded. Six varieties of fish species and four types of insects are found to be prevalent for catching carnivorous fishes. Five specially modified indigenous types of bait moulded with fish attractants were also documented. Bait-fish species association in hook and line fishery of river Ganga is discussed. Feeding habits of the target fishes was compared with the type of baits employed. Conservation issues associated with hook and line fishery is highlighted along with possible remedial measures. Different varieties of hook &amp; line fishery which are in operation in river Ganga are briefly described. Indigenous Traditional Knowledge (ITK) associated with hook &amp; line fishery needs to be properly documented and preserved for developing and encouraging ‘sport fishery’ in River Ganga

Bait specificity in Hook and line fishery of River Ganga and associated conservation issues

61-72Recent survey in lower 1,110 km stretch of River Ganga regarding ‘hook and line’ fishery revealed that fishers apply their inherited indigenous knowledge for selection of bait to harvest finfish and shellfish from river water. A total number of 26 different types of baits under 07 categories were recorded. Six varieties of fish species and four types of insects are found to be prevalent for catching carnivorous fishes. Five specially modified indigenous types of bait moulded with fish attractants were also documented. Bait-fish species association in hook and line fishery of river Ganga is discussed. Feeding habits of the target fishes was compared with the type of baits employed. Conservation issues associated with hook and line fishery is highlighted along with possible remedial measures. Different varieties of hook & line fishery which are in operation in river Ganga are briefly described. Indigenous Traditional Knowledge (ITK) associated with hook & line fishery needs to be properly documented and preserved for developing and encouraging ‘sport fishery’ in River Ganga

Chemical applications of hyper-Rayleigh scattering in solution

Hyper-Rayleigh or second harmonic Rayleigh scattering (HRS or SHLS) has been employed to measure equilibrium physical properties of molecules in solution. It has been utilized in our laboratory to obtain the dissociation constants of weak organic acids such as substituted benzoic and cinnamic acids in solution. Partition coefficient, supramolecular structure formation and stoichiometry, critical micelle concentration, and binding or association constant of a molecule with another molecule have all been measured by the HRS technique by us. We find that both the symmetry of the molecule and its concentration in the medium play an important role in finding new chemical applications of the technique

'Holy grails' of chemistry: the transition state in chemical reaction

In discussions of chemical reactions, particularly their rates, the concept of a 'transition state' appears frequently. In all undergraduate textbooks in chemistry, the notion of a transition state (henceforth abbreviated as TS) or an activated complex (synonymous) is used in describing the passage of a reaction from reactants to products. However, everyone understands and interprets the exact meaning of the term, TS, in one’s own way. In this article, I shall attempt to develop the concept and try to provide a working definition for the TS in a chemical reaction

Chemical Applications of Hyper-Rayleigh Scattering in Solution

Hyper-Rayleigh or second harmonic Rayleigh scattering (HRS or SHLS) has been employed to measure equilibrium physical properties of molecules in solution. It has been utilized in our laboratory to obtain the dissociation constants of weak organic acids such as substituted benzoic and cinnamic acids in solution. Partition coefficient, supramolecular structure formation and stoichiometry, critical micelle concentration, and binding or association constant of a molecule with another molecule have all been measured by the HRS technique by us. We find that both the symmetry of the molecule and its concentration in the medium play an important role in finding new chemical applications of the technique

Second harmonic generation in some donor-acceptor ethylenes-I

We report the absorption spectra, oscillator strengths, ground state and excited state dipole moments, and molecular second order polarizability coefficients (β<SUP>CT</SUP>) due to donor-acceptor charge transfer in four trisubstituted ethylenes, namely 1,1-bisdimethylamino-2-nitroethylene, 1,1-bispyrolidino-2-nitroethylene, 1,1-bispiperidino-2-nitroethylene and 1,1-bismorpholino-2-nitroethylene. The results are compared with that of trans-N,N-dimethylamino-nitroethylene, which has a large β<SUP>CT</SUP>. The powder second harmonic generation (SHG) intensity of all these molecules is also measured and only 1,1-bispiperidino-2-nitroethylene is found to possess an efficiency of 20% of that of urea under the same conditions. The SHG efficiency of this compound and deficiency in the other molecules in the powdered state is discussed in terms of their arrangements in the unit cell. The crystal structure of the active molecule is also presented and the structure-property relationship is critically examined in all these molecules

I∗I^* production from n-alkyl iodides at 222 nm

The dynamics of $I^*(^2P_{1/2})$ production in a series of n-alkyl iodides at 222 nm have been investigated. Data are analyzed using a simple classical impulsive model. At this excitation wavelength, $I(^2P_{3/2})$ originates from a curve-crossing between the $^3Q_0$ and $^1Q_1$ surfaces and the probability of crossing for all the iodides has been derived. Since the $I^*$ quantum yield is found to decrease, the probability of crossing increases as a function of the alkyl radical size, which is also consistent with the classical model