OBSERVATION OF NANOMETER-LEVEL STRUCTURAL-CHANGES BY THE TRANS-CIS TRANSITION OF AN AZOBENZENE DERIVATIVE MONOLAYER WITH A RADIOACTIVE-TRACER

We report direct observation of radioisotopically labeled molecular st ructural changes in these photochemical processes with the interferenc e effect of electron-capture X-ray emitted by nuclear transformations in radioactive atoms. The azobenzene derivative molecules were specifi cally reacted with the radioactive atoms (In-111) by using ionic bonds between the carboxyl groups in the azobenzene derivatives and the rad ioactive atoms. The trans-cis isomerization of the monolayer on the su bstrate was distinctly reflected in the period of the observed interfe rence fringes. We measured the trans-cis photoisomerizations on the sa me substrate during seven alternations by using UV-visible light irrad iation. As a result, we observed irreversible photochromism in the mon olayer of azobenzene derivatives on the substrate because of the close packing of chromophores.