P K Chakraborti
Articles written in Pramana – Journal of Physics
Volume 11 Issue 3 September 1978 pp 307-311 Experimental Techniques And Instrumentation
By means of refinements in the modulated molecular beam technique the signal-to-noise ratio can be greatly improved, and differential cross-sections, for collision of molecuies of the same species, can be measured. This was accomplished by combining beam modulation and phase sensitive detection with very sharp turning on the front end of the lock-in-amplifier and long integration times on the output. In addition, the signal-to-noise ratio of the Ar-Ar system as a function of integration time was investigated using two different types of electron bombardment detectors an Aberth ion-source and a quadrupole mass filter. With an integration time of 40 min the estimated upper limit to the signal-to-noise ratio is 1500 to 1 for the Aberth ion-source. Using quadrupole mass filter with an integration time of 60 min the estimated upper limit to the signal-to-noise ratio is 5 × 104 to 1. For chemical kinetics studies this ratio may be two orders of magnitude higher.
Volume 25 Issue 2 August 1985 pp 191-200 Atomic And Molecular Physics
Supersonic expansion from a nozzle produces noble gas clusters under various source conditions. The characteristics of atoms and dimers in a nozzle beam are examined. A study of the dimer collision cross-section suggests the existence of a temperature-dependent limiting oven pressure (
Volume 37 Issue 6 December 1991 pp 539-544 Research Articles
A new technique has been developed to measure isotope shifts of high-lying atomic levels using multi-step photoionization. This technique has been demonstrated with the measurement of isotope shift between235U and238U isotopes in the energy level at 34372.992 cm−1. The value of isotope shift thus measured matches well with the value reported in literature.
Volume 38 Issue 4 April 1992 pp 397-409
Time-of-flight technique has been used to characterize supersonic beams of polyatomic molecules in terms of translational and vibrational temperatures, various velocity parameters and speed ratio. Collision effectiveness and effective specific heat ratio of polyatomic gases pertinent to jet expansion have also been determined and interpreted.
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