Non-equilibrium H-2 ortho-to-para ratio in two molecular clouds of the Galactic Center

We present ISO observations of the S(0), S(1), S(2), and S(3) rotational li nes of molecular hydrogen from two molecular clouds near the Galactic Cente r (GC). We have also measured continuum dust emission at infrared wavelengt hs with ISO and the rotational radio lines J=1-0 of (CO)-C-13 and (CO)-O-18 and J=2-1 of (CO)-O-18 With the IRAM-30m telescope. Using the dust continu um spectra and the CO lines we derive a total visual extinction of similar to 15-20 magnitudes toward these GC clouds. After correcting the Hz data fo r extinction, the gas temperatures are similar to 250 K and the column dens ities of warm gas are similar to 2 X 10(21) cm(-2). This is the first direc t measure of the H-2 column densities of the warm component; with this, we estimate an NH3 abundance in the warm gas of similar to 2 10(-7). The colum n density of warm gas is, at least, a factor of 100 larger than the corresp onding column densities derived from the warm dust. The observed ortho-to-p ara ratio (OTPR) is similar to 1, clearly below the local thermodynamical e quilibrium (LTE) OTPR for gas at 250 K of similar to 3. Low velocity shocks (similar to 10 km s(-1)) are the most likely explanation far the column de nsities of warm gas and dust and the non-LTE H-2 OTPR.