Knowledge Bank

In the interpretation of Stack modulation spectra obtained using phase sensitive detection methods it becomes necessary to establish the. effect of modulation broadening on absorption and emission lines; to determine the differences, advantages, and optimal modulation conditions for detection at the fundamental and at twice the fundamental; to establish procedures of extracting the. change in dipole moment $|\Delta \mu |$ and change in polarizability $|\Delta \alpha |$ between the ground and an excited electronic state; and to examine the mixing of states using phase sensitive detection. Closed, analytical expressions for the Fourier coefficients (amplitudes) which arise in Stark modulation of unsaturated Lorentzian ion absorption or emission lines for the case where $|\Delta \mu |\ne 0,|\Delta \alpha |=0$ have been developed and used in examining the aforementioned points. In addition, the expressions have been tested under actual experimental conditions for the lowest two $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi \Pi \ast$ states of azulene (substituted in naphthalene), Limitations on the points discussed above are also established for the case $|\Delta \alpha |\ne 0,|\Delta \mu |\ge 0$ by evaluating the Fourier coefficients using a Romberg integration technique.