Part I. Application of the Fabry-Perot interferometer for high resolution studies Part II. Hyperfine structure in bromine

PART I: The Fabry-Perot interferometer is generally used in transmission. It is described how it can be modified so that the fringes can be used in reflection. The general theory of the reflection fringes is considered. It is shown that the interferometer used in reflection is about 30 times faster in light speed than one used intransmission. It is shown how the technique can beadopted to the measurement of wavelengths and to the evaluation of the line-widths of lines from weak sources. PART II: Hyperfine structure examinations are carried out over the range 6000 to 3700 in the arc spectrum of bromine and over the range 5500 to 3900 in the spark spectrum of bromine. Twenty-one lines in the arc spectrum of bromine are examined. Eighteen classified and twenty unclassified lines in Br II spectrum are measured for the first time and hyperfine structure term interval factors are derived for fourteen terms in thespark spectrum of bromine. The theory of the hyperfine structure analysis is considered in brief. Both the arc and the spark spectra are obtained by employing a circulating system and a high frequency oscillator. The analysis of the lines fits well the term scheme. A few anomalies have been noted and have been accounted for, some of them being due to faulty interpretations of the lines by previous workers. Deviations from the interval rule occur in the arc spectrum of bromine and these are completely explained by the existence of an electrical quadrupole moment of nuclei for both the bromine isotopes. The coupling constants for the terms concerned are determined from the term values and using these, both the quadrupole moment and the magnetic moment of the bromine nucleus are evaluated.