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Michael
D. Morse PHYSICAL CHEMISTRY Professor (b. 1952) |
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Awards and Activities Research Interests Research in Professor Morse's group is directed
toward understanding the chemical bonding and electronic structure in
metallic and semiconductor systems by detailed spectroscopic investigations. This research makes extensive use of laser
spectroscopy through laser-induced fluorescence, resonant two-photon ionization,
and zero electron kinetic energy photoelectron spectroscopic techniques. In these experiments, metal or semiconductor atoms are ablated
from an appropriate target in the throat of a pulsed supersonic expansion
by a focused laser pulse. Condensation of the atomic species then occurs
in the high-pressure region downstream from the point of vaporization. Expansion into vacuum cools the molecules to a few Kelvin, then
isolates them from further collisions as the pressure drops. Farther downstream, a variety of spectroscopic experiments are
performed, aimed at understanding the molecular structure (both electronic
and geometrical) of the small metal molecules. One spectroscopic technique used is resonant
two-photon ionization spectroscopy (R2PI). In this method, a tunable dye laser is scanned in conjunction with
a fixed frequency excimer laser. The
excimer laser wavelength is chosen so that it cannot ionize the ground
state of the molecule with a single photon, but the combination of one
dye laser photon plus one excimer laser photon is sufficient for ionization. Under these conditions an enhancement of the ion signal is observed
in a mass spectrometer whenever the dye laser is resonant with a molecular
absorption. By detecting the ions in a mass spectrometer we can identify the
mass of the absorber. In these
spectroscopic studies it is possible to measure vibrational frequencies,
bond lengths, electronic state symmetries, and bond strengths of many
novel species. Among the molecules first studied in our group are Si2N,
MoC, PdC, NbCr, YCu, Ti2, GaAs, LiCu, AlNi, Au3,
Al3, Bi3, and CuAgAu. More recently we have recorded electronic spectra of unsaturated
organometallic molecules including CrCH3, CrCCH, and NiCH3. These are among the most complex unsaturated transition-metal ligand
molecules ever spectroscopically studied in the gas phase. |
We also have the ability to study molecules using a cw ring
dye laser, which provides an instrumental resolution of better than 0.003
cm-1, This permits the study of finer details such
as hyperfine interactions and electric dipole moments. Research in the Morse group is also directed
toward extending supersonic jet techniques to include other spectroscopies
and other types of molecules. In
one such extension, Professor Peter Armentrout and I have built a pulsed-field
ionization, zero electron kinetic energy (PFI-ZEKE) photoelectron spectrometer
to provide detailed information about the electronic states of transition
metal containing cations. In our
first experiment we have measured the ionization energy of YO to be 49305 1
cm-1, and the bond length of YO+ to be 1.75 0.01
Å. Work is now in progress to
extend these studies to other molecular ions, such as Cr2+,
Cu3+, and others. Finally, another experiment is currently under construction to
perform direct IR absorption spectra of gaseous unsaturated transition
metal carbonyls, such as NiCO, CrCO, Cr(CO)2, etc. Selected Publications
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