We have used the Long Wavelength Spectrometer aboard the Infrared Space Obs
ervatory to map the far-infrared continuum emission (45-175 mum) toward sev
eral massive giant molecular cloud (GMC) cores located near the Galactic ce
nter. The observed far-infrared and submillimeter spectral energy distribut
ions imply low temperatures (similar to 15-22 K) for the bulk of the dust i
n all the sources, which is consistent with external heating by the diffuse
interstellar radiation field (ISRF) and suggests that these GMCs do not ha
rbor high-mass star formation sites, despite their large molecular mass. Ob
servations of far-infrared atomic fine-structure lines of C II and O I indi
cate an ISRF enhancement of similar to 10(3) in the region. Through continu
um radiative transfer modeling, we show that this radiation field strength
is in agreement with the observed far-infrared and submillimeter spectral e
nergy distributions, assuming primarily external heating of the dust with o
nly limited internal luminosity (similar to2 x 10(5) L.). Spectroscopic obs
ervations of millimeter-wave transitions of H2CO, CS, and (CS)-S-34 carried
out with the Caltech Sub-millimeter Observatory and the Institut de Radio
Astronomie Millimetrique (IRAM) 30 m telescope indicate a gas temperature o
f similar to 80 K, which is significantly higher than the dust temperature,
and a density of similar to1 x 10(5) cm(-3) in GCM 0.25+0.01, the brightes
t submillimeter source in the region. We suggest that shocks caused by clou
d collisions in the turbulent interstellar medium in the Galactic center re
gion are responsible for heating the molecular gas. This conclusion is supp
orted by the presence of widespread emission from molecules such as SiO, SO
, and CH3OH, which are considered good shock tracers. We also suggest that
the GMCs studied here are representative of the "typical," pre-star-forming
cloud population in the Galactic center.