A modified thin lens spectrometer has been used with improved geometry. The focussing properties of the instrument have been investigated for various geometries. Using this instrument the conversion electron spectra of Sn¹¹³ and Sb¹²⁵ have been taken. The intensity of the 256 kev conversion line in Sn¹¹³ spectrum showed that this transition is predominantly M1 in character and therefore the spin and parity of 648-kev level in In¹¹³ should be 1/2¯ or 3/2¯. The low energy part of the conversion spectrum of Sb¹²⁵showed the presence of the K conversion lines of 76 kev and 143 kev transitions, not observed before. The presence of these conversion lines confirmed the existence of a weak beta group feeding a level at 540 kev in the excited state of Te¹²⁵. The energy levels of Cs¹³³ have been studied through the decay of Ba¹³³. Scintillation spectra (using NaI(T1 ) crystal) together with photoelectron, conversion and e-gamma coincidence spectra have been taken. An analysis of the results indicate that the ground state and 81, 161, 383 and 437 kev levels in Cs¹³³ have spins and parities of 7/2⁺, 5/2⁺,5/2⁺,3/2⁺, 1/2⁺ respectively. The multipolarities of the connecting transitions are 383 kev (E2 ), 356 (E2 ) 302 kev (M1 with E2 admixture)} 276 kev (E2 ), 161 kev (probably M1 ) Electron capture from Ba¹³³ is limited almost entirely to the 437 and 383 kev levels in Cs¹³³, The decay energy available for capture to the 437 level is approximately 50 kev. / Science, Faculty of / Physics and Astronomy, Department of / Graduate