10,129 research outputs found
Theory of resonantly enhanced multiphoton processes in molecules
In this paper we formulate a theory for the analysis of resonant enhanced multiphoton ionization processes in molecules. Our approach consists of viewing the (n+m) photon ionization process from an isotropic initial state as mâphoton ionization out of an oriented, excited state. The orientation in this resonant state, which is reached by nâphoton excitation from the initial state, is nonisotropic, and is characteristic of this absorption process. The ionization simply probes this anisotropic population. The calculation of the REMPI process thus consists of determining the anisotropy created in the resonant state and then coupling this anisotropic population to ionization out of it. While the former is accomplished by the solution of appropriate density matrix equations, the latter is done by coupling these density matrix elements to angleâresolved ionization rates out of this state. An attractive feature of this approach is that the influence of saturation effects, and other interactions, such as collisions, on the photoelectron properties is easily understood and incorporated. General expressions are derived for photoelectron angular distributions. Based on these, several properties of the angular distributions that follow purely on symmetry considerations are discussed. One of the new features that emerge out of this work is the saturation induced anisotropy in REMPI. In this effect higher order contributions to the angular distributions appear since saturation influences different ionization channels differently thereby creating an additional anisotropy in the excited state
Evaluation of functioning of ICDS project areas under Indore and Ujjain divisions of the state of Madhya Pradesh
Background: Integrated Child Development Services (ICDS) is recognized worldwide as one of the most efficient community based programmes promoting early childhood care. Regular evaluations of the programme have been conducted to make it more effective and adequate for the beneficiaries. Objectives: To evaluate the functioning of the Anganwadi Centers under different project areas of Indore and Ujjain Divisions. Methods: Under the present evaluation system one ICDS project and five Anganwadi Centers under the project area (AWCs) were visited on a monthly basis and services provided reviewed. Findings reported are from nine project areas under Indore and Ujjain Divisions in the state of Madhya Pradesh from October 2008 â June 2009. Results: A total of 45 centers were evaluated. 29 centers were operating from rented buildings and storage facilities were lacking at 19 of the centers. Though the quality of food was acceptable to the beneficiaries shortage of food was a problem at the centers. Absence of Pre-School Education (PSE) and Nutrition and Health Education (NHED) Kits compromised PSE and NHED activities at the centers. Unavailability of medicine kits, lack of regular visits by the ANMs to the centers and absence of routine health check up of beneficiaries were other problems encountered under the project areas surveyed. Availability of a doctor under each project area was stated as a major need by the workers. Conclusion: Coordinated steps catering to different services provided at the centers are needed to optimize the functioning of the ICDS scheme
Rotational branching ratios at low photoelectron energies in resonant enhanced multiphoton ionization of NO
We report calculated rotational branching ratios for very low energy (50 meV) photoelectrons resulting from (1+1âČ) resonant enhanced multiphoton ionization (REMPI) via the J_i =1/2, 3/2, 5/2, and 7/2 levels of the P_(11) branch of the Aâ^2ÎŁ^+ (3sÏ) state of NO. Even angular momentum transfer (ÎNâĄN_+âN_i) peaks are dominant in these rotational distributions, in agreement with the selection rule ÎN+l=odd. Angular momentum coupling in the photoelectron wave function arising from the molecular ion potential leads to smaller but appreciable ÎN=odd peaks. The calculated ÎN=0 to ÎN=+2 peak ratios show the same strong decrease when J_i increases from 1/2 to 3/2 as seen in the experimental zeroâkineticâenergy (ZEKE) photoelectron spectra [Sander et al., Phys. Rev. A 36, 4543 (1987)], but do not show the rapid dieâoff of the ÎNâ 0 peaks for higher J_i observed experimentally. The calculated trend in the ÎN=+2 vs ÎN=0 peaks could be understood on the basis of simple angular momentum transfer arguments. These same arguments indicate that this trend in the ÎN=0 and +2 peaks with increasing angular momentum is not generally expected in other branches. Spectra via the R_(21) (âJ) branch are presented to support this assertion. We also present photoelectron angular distributions which show a strong dependence on ÎN reflecting the changing composition of the photoelectron wave function
Psychological Morbidity in Students of Medical College and Science and Art College Students - A Comparative Study
Considering the importance of quality of life in medical students we have conducted a cross sectional & descriptive study on screening of mental illness of 60 medical students of prefinal year and comparing it with 60 students of third year of Science and Art College. Students were selected via random sampling. GHQ-12 was used as a screening tool and after obtaining scores students were graded in 3 categories - individuals screened positive for psychological morbidity were of Grades 2 and 3 and individuals screened negative for psychological morbidity were of Grade 1 and they were compared according to college, gender & residence. Students screened positive for psychological morbidity as per GHQ-12 were found higher in medical college (87%) as compared to Science and Art College (45%) and a statistically significant association was found between psychological morbidity and medical students. Psychological morbidity was not significantly associated with residence and gender
Three-photon resonant four-photon ionization of H_2 via the C^1 â_u state
Ab initio calculations are presented for the vibrational branching ratios in three-photon resonant four-photon ionization of H_2 via the C^1Î _u state. Energy and internuclear distance dependences of the boundfree electronic transition matrix element are explicitly included to estimate deviations from the Franck-Condon approximation. While our calculated branching ratios confirm certain important trends seen experimentally, some differences remain
Extraction of alignment parameters from circular dichroic photoelectron angular distribution (CDAD) measurements
In a previous paper, we showed that circular dichroism in photoelectron angular distributions (CDAD) can be used to probe alignment in gas phase atoms and linear molecules. Often this alignment is parametrized through the moments of alignment A(2), A(4), etc., which are commonly extracted from fluorescence polarization measurements. In this paper we show how these can be simply extracted from CDAD spectra. This technique can be used in principle to extract the moments to any order
(1+ 1) CDAD: A new technique for studying photofragment alignment
We report a new technique for measuring photofragment alignment in the gas phase by observing circular dichroism in photoelectron angular distributions (CDAD). This technique is well suited for determining the gas phase alignment of linear molecules. The experiment involves excitation of the photofragment with linearly polarized light followed by photoionization with left or right circularly polarized light. The difference between the photoelectron angular distributions for these two cases is the CDAD spectrum. By measuring CDAD through two different excitation branches, one can obtain the ground state photofragment alignment A(2)0 using a simple analytical formula independent of the photoionization dynamics
Micromegas TPC studies at high magnetic fields using the charge dispersion signal
The International Linear Collider (ILC) Time Projection Chamber (TPC)
transverse space-point resolution goal is 100 microns for all tracks including
stiff 90 degree tracks with the full 2 meter drift. A Micro Pattern Gas
Detector (MPGD) readout TPC can achieve the target resolution with existing
techniques using 1 mm or narrower pads at the expense of increased detector
cost and complexity. The new MPGD readout technique of charge dispersion can
achieve good resolution without resorting to narrow pads. This has been
demonstrated previously for 2 mm x 6 mm pads with GEMs and Micromegas in cosmic
ray tests and in a KEK beam test in a 1 Tesla magnet. We have recently tested a
Micromegas-TPC using the charge dispersion readout concept in a high field
super-conducting magnet at DESY. The measured Micromegas gain was found to be
constant within 0.5% for magnetic fields up to 5 Tesla. With the strong
suppression of transverse diffusion at high magnetic fields, we measure a flat
50 micron resolution at 5 Tesla over the full 15 cm drift length of our
prototype TPC.Comment: 7 pages, 3 figure
Resonant enhanced multiphoton ionization studies of atomic oxygen
In resonant enhanced multiphoton ionization (REMPI), an atom absorbs several photons making a transition to a resonant intermediate state and subsequently ionizing out of it. With currently available tunable narrow-band lasers, the extreme sensitivity of REMPI to the specific arrangement of levels can be used to selectively probe minute amounts of a single species (atom) in a host of background material. Determination of the number density of atoms from the observed REMPI signal requires a knowledge of the multiphoton ionization cross sections. The REMPI of atomic oxygen was investigated through various excitation schemes that are feasible with available light sources. Using quantum defect theory (QDT) to estimate the various atomic parameters, the REMPI dynamics in atomic oxygen were studied incorporating the effects of saturation and a.c. Stark shifts. Results are presented for REMPI probabilities for excitation through various 2p(3) (4S sup o) np(3)P and 2p(3) (4S sup o) nf(3)F levels
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