  We extend the concepts of the Autler-Townes doublet and triplet spectroscopy
to quartuplet, quintuplet and suggest linkages in sodium atom in which to
display these spectra. We explore the involved fundamental processes of quantum
interference of the corresponding spectroscopy by examining the Laplace
transform of the corresponding state-vector subjected to steady coherent
illumination in the rotating wave approximation and Weisskopf-Wigner treatment
of spontaneous emission as a simplest probability loss. In the quartuplet, four
fields interact appropriately and resonantly with the five-level atom. The
spectral profile of the single decaying level, upon interaction with three
other levels, splits into four destructively interfering dressed states
generating three dark lines in the spectrum. These dark lines divide the
spectrum into four spectral components (bright lines) whose widths are
effectively controlled by the relative strength of the laser fields and the
relative width of the single decaying level. We also extend the idea to the
higher-ordered multiplet spectroscopy by increasing the number of energy levels
of the atomic system, the number of laser fields to couple with the required
states. The apparent disadvantage of these schemes is the successive increase
in the number of laser fields required for the strongly interactive atomic
states in the complex atomic systems. However, these complexities are naturally
inherited and are the beauties of these atomic systems. They provide the
foundations for the basic mechanisms of the quantum interference involved in
the higher-ordered multiplet spectroscopy.
