“…Quite recently, we reported the results of our infrared work on the m 12 band of 13 C 12 CH 4 [1], the m 7 band of cis-C 2 H 2 D 2 [2], and the m 3 and m 6 bands of C 2 H 3 D in separate single-state analyses [3,4]. As part of our ongoing infrared investigation on ethylene, specifically on the isopotomer C 2 H 3 D, we report in this note the results of the analysis we did on the m 12 band of C 2 H 3 D. In addition to the improved overall accuracy of the rovibrational constants, more higher-order upper state constants were derived in this analysis.…”