Understanding highly excited states via parametric variations

Highly excited vibrational states of an isolated molecule encode the vibrational energy flow pathways in the molecule. Recent studies have had spectacular success in understanding the nature of the excited states mainly due to the extensive studies of the classical phase space structures and their bifurcations. Such detailed classical-quantum correspondence studies are presently limited to two or quasi two dimensional systems. One of the main reasons for such a constraint has to do with the problem of visualization of relevant objects like surface of sections and Wigner or Husimi distributions associated with an eigenstate. This neccesiates various alternative techniques which are more algebraic than geometric in nature. In this work we introduce one such method based on parametric variation of the eigenvalues of a Hamiltonian. It is shown that the level velocities are correlated with the phase space nature of the corresponding eigenstates. A semiclassical expression for the level velocities of a single resonance Hamiltonian is derived which provides theoretical support for the correlation. We use the level velocities to dynamically assign the highly excited states of a model spectroscopic Hamiltonian in the mixed phase space regime. The effect of bifurcations on the level velocities is briefly discussed using a recently proposed spectroscopic Hamiltonian for the HCP molecule.Comment: 12 pages, 9 figures, submitted to J. Chem. Phy

Exploring the influence of iron substitution in lithium rich layered oxides Li2Ru1-:XFexO3: Triggering the anionic redox reaction

Lithium rich layered materials are an interesting class of materials which exploit both anionic and cationic redox reactions to store energy upwards of 250 mA h g-1. This paper aims to understand the nature of the redox reactions taking place in these compounds. Li2RuO3 was used as the base compound, which is then compared with compounds generated by partially substituting Ru with Ti and Fe respectively. Electrochemical tests indicate that Fe substitution in the sample leads to an improvement in capacity, cycle life and reduction of potential decay. To elucidate the reason for this improvement in operando diffraction experiments were carried out, highlighting the formation of a secondary de-lithiated phase. The distortion of the pristine structure eventually induces frontier orbital reorganization leading to the oxygen redox reaction resulting in extra capacity. Local changes at Fe and Ru ions are recorded using in operando X-ray absorption spectroscopy (XAS). It was noted that while Ru undergoes a reversible redox reaction, Fe undergoes a significant irreversible change in its coordination environment during cycling. The changes in the coordination environment of oxygen and formation of O2n- type species were probed in situ using soft X-rays

Neutral point clamped quasi Z source inverter for photovoltaic systems

Multilevel inverters are becoming popular for power conversion in renewable energy systems, AC-DC hybrid micro grids etc. The voltage stress and inrush current through these inverter leg switches are quite higher as compared to the load ratings which increase the chances of inverter leg switch failure. A three level neutral point clamped quasi Z source inverter topology is discussed in this paper which has the features of lower component count, reduced capacitor voltage stress, and it can be operated at different control strategies to achieve wide range of voltage boosting ability, suited for photovoltaic (PV) systems. It also ensures continuous input current irrespective of the DC supply voltage variations and injects stable and smooth power to the load/grid. The effectiveness of the proposed inverter is verified by simulation results in MATLAB Simulink model as well as performing experiment with the help of a laboratory prototype

Performance evaluation of roof top solar photovoltaic systems in Tamilnadu

This manuscript reports the monitored performance results of roof top solar photovoltaic (PV) power plants in different parts of Tamilnadu, India. In this work, PV plants of capacities 84 kWp and 18 kWp located at Tirunelveli and Ranipet respectively in Tamilnadu are considered. During an eight month period, of September 2014 to April 2015, these plants had generated 43.99 MWh and 15.55 MWh units of electricity respectively. The average electricity production per day for the considered period of these plants is 181.74 kWh and 62.81 kWh respectively. The performance ratio (PR) of these plants PV1 and PV2 is found to be 0.52 and 0.86 respectively. The characteristics of poly crystalline PV modules and the performance of employed photovoltaic inverters are also analyzed.It is observed that external conditions like climate and bad weather significantly reduces the PV system output, whereas it reduces marginally due to inverter failure as observed from the values of energy yield and performance ratio of these plants. Online monitoring of PV plant with DC/AC line and phase voltages and current waveforms observed for the given day are also presented

Experimental Verification of Single Phase Z Source Inverter for Photovoltaic Applications

A single phase Z source inverter is developed for better voltage boosting and inversion ability suited for photovoltaic power generation systems. The operation of the Z source inverter is described with relevant equations. Simple boost scheme is used for switching actions of the inverter. The performance of the inverter used for photovoltaic applications can be checked with simulation and experimental results, which prove that it has single-stage buck and boost capability and improved reliability

Exploring the influence of iron substitution in lithium rich layered oxides Li2Ru1-xFexO3: triggering the anionic redox reaction

Lithium rich layered materials are an interesting class of materials which exploit both anionic and cationic redox reactions to store energy upwards of 250 mA h g−1. This paper aims to understand the nature of the redox reactions taking place in these compounds. Li2RuO3 was used as the base compound, which is then compared with compounds generated by partially substituting Ru with Ti and Fe respectively. Electrochemical tests indicate that Fe substitution in the sample leads to an improvement in capacity, cycle life and reduction of potential decay. To elucidate the reason for this improvement in operando diffraction experiments were carried out, highlighting the formation of a secondary de-lithiated phase. The distortion of the pristine structure eventually induces frontier orbital reorganization leading to the oxygen redox reaction resulting in extra capacity. Local changes at Fe and Ru ions are recorded using in operando X-ray absorption spectroscopy (XAS). It was noted that while Ru undergoes a reversible redox reaction, Fe undergoes a significant irreversible change in its coordination environment during cycling. The changes in the coordination environment of oxygen and formation of O2n− type species were probed in situ using soft X-rays