In April 1898, through a systematic search of substances, she finds that thorium compounds, like those of uranium, emitted "Becquerel rays", thus preceding the work of Frederick Soddy and Ernest Rutherford on the nuclear decay of thorium to radium by three years.[4] 1897 – Ivan Borgman demonstrates that X-rays and radioactive materials induce thermoluminescence. 1897 – J. J. Thomson's experimentation with cathode rays led him to suggest a fundamental unit more than a 1,000 times smaller than an atom, based on the high charge-to-mass ratio.