You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Fundamental and Torsional Combination Bands of Two Isomers of the OCS-CO(2) Complex in the CO(2) ν(3) Region. Spectra of two isomers of the weakly bound complex OCS-CO(2) are observed in the region of the CO(2) ν(3) fundamental vibration (∼2349 cm(-1)), using an infrared tunable diode laser to probe a pulsed supersonic slit-jet expansion. Two bands are measured and analyzed for each isomer, the fundamental asymmetric stretch of the CO(2) component and a combination band involving this fundamental plus the intermolecular out-of-plane torsional mode. For one isomer, the corresponding torsional combination band is also detected in the OCS ν(1) stretching region (∼2060 cm(-1)). The resulting torsional frequencies are found to be 18.8 and 15.9 cm(-1) for isomers a and b of OCS-CO(2), respectively. This may be the first time that such a combination band is observed for a higher-energy isomer of a weakly bound complex.
{"Chemical": ["CO(2)", "OCS"]}