We present Spitzer IRS spectra ( R \sim 600 , 10 – 38 µm ) of 38 positions in the Galactic Center ( GC ) , all at the same Galactic longitude and spanning \pm 0.3 ^ { \circ } in latitude .
Our positions include the Arches Cluster , the Arched Filaments , regions near the Quintuplet Cluster , the “ Bubble ” lying along the same line-of-sight as the molecular cloud G0.11 - 0.11 , and the diffuse interstellar gas along the line-of-sight at higher Galactic latitudes .
From measurements of the [ O iv ] , [ Ne ii ] , [ Ne iii ] , [ Si ii ] , [ S iii ] , [ S iv ] , [ Fe ii ] , [ Fe iii ] , and H _ { 2 } S ( 0 ) , S ( 1 ) , and S ( 2 ) lines we determine the gas excitation and ionic abundance ratios .
The Ne/H and S/H abundance ratios are \sim 1.6 times that of the Orion Nebula .
The main source of excitation is photoionization , with the Arches Cluster ionizing the Arched Filaments and the Quintuplet Cluster ionizing the gas nearby and at lower Galactic latitudes including the far side of the Bubble .
In addition , strong shocks ionize gas to O ^ { +3 } and destroy dust grains , releasing iron into the gas phase ( Fe/H \sim 1.3 \times 10 ^ { -6 } in the Arched Filaments and Fe/H \sim 8.8 \times 10 ^ { -6 } in the Bubble ) .
The shock effects are particularly noticeable in the center of the Bubble , but O ^ { +3 } is present in all positions .
We suggest that the shocks are due to the winds from the Quintuplet Cluster Wolf-Rayet stars .
On the other hand , the H _ { 2 } line ratios can be explained with multi-component models of warm molecular gas in photodissociation regions without the need for H _ { 2 } production in shocks .