Knowledge Bank

We have used single- and double-resonance vibrational overtone excitation, together with Infrared Laser Assisted Photofragment Spectroscopy (IRLAPS) dectection to measure highly resolved spectra of jet-cooled methanol molecules in levels ranging from $VOH=2-8$. The single resonance spectra provide the overall picture of the strongest anharmonic resonances affecting OH stretch vibration, and studies on a number of deuterated isotopomers confirm the assignments of these resonances. These strong couplings define the ultrafast dynamics that the molecule would undergo if certain OH stretch bands were coherently excited. Double-resonance vibrational overtone excitation of jet-cooled methanol produces fully rotationally resolved spectra which reveal finer splittings reflecting the longer time dynamics. These spectra show that the longer time dynamics are a sensitive function of energy. Double resonance studies of the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}C$ substituted molecule confirm that the energy sensitivity arises from the relative sparsity of low order resonances, even at vibrational energies where the total density of states is high.