Cj. Gruenloh et al., RESONANT ION-DIP INFRARED-SPECTROSCOPY OF THE S-4 AND D-2D WAFER OCTAMERS IN BENZENE-(WATER)(8) AND BENZENE(2)-(WATER)(8), The Journal of chemical physics, 109(16), 1998, pp. 6601-6614
The techniques of resonant two-photon ionization (R2PI), W-UV (ultravi
olet) hole-burning, and resonant ion-dip infrared (RIDIR) spectroscopi
es have been employed along with density functional theory (DFT) calcu
lations to assign and characterize the hydrogen-bonding topologies of
two isomers each of the benzene-(water)(8) and (benzene)(2)(water)8 ga
s-phase clusters. The BW8 isomers (B = benzene, W = water) have R2PI s
pectra which are nearly identical to one another, but shifted by about
5 cm(-1) from one another. This difference is sufficient to enable in
terference-free RIDIR spectra to be recorded. As with smaller BWn clus
ters, the BW8 clusters fragment following photoionization by loss of e
ither one or two water molecules. The OH stretch IR spectra of the two
BW8 isomers bear a close resemblance to one another, but differ most
noticeably in the double-donor OH stretch transitions near 3550 cm(-1)
. Comparison to DFT calculated minimum energy structures, vibrational
frequencies, and infrared intensities leads to an assignment of the H-
bonding topology of the BW8 isomers as nominally cubic water octamers
of S-4 and D-2d symmetry surface attached to benzene through a pi H-bo
nd, A series of arguments based on the R2PI and hole-burning spectra l
eads to an assignment of additional features in the R2PI spectra to tw
o isomers of B2W8. The OH stretch RIDIR spectra of these isomers show
them to be the corresponding S-4 and D-2d analogs of B2W8 in which the
benzene molecules each form a pi H-bond with a different dangling OH
group on the W-8 sub-cluster. (C) 1998 American Institute of Physics.
[S0021-9606(98)00140-8].