Table A1. Observed transitions of C2D4 dimer, with calculated values in parentheses for obscured or weak lines (in units of 1/cm) *asterisks indicate the Q-branch transitions which tend to be strong. **the 2202.07 line appears to be partly resolved into two components. In general, each line has a number of contributing transitions. The J, K assignments indicate the strongest contribution to each line. ************************************************ J' K' J" K" Position ************************************************ 4 2 5 3 2197.8127 3 2 4 3 (2197.937) 2 2 3 3 2198.0562 (very broad ~0.013) 6 1 7 2 2198.1755 5 1 6 2 (2198.303) 4 1 5 2 (2198.425)* 3 1 4 2 2198.5463 2 1 3 2 2198.6705 1 1 2 2 2198.7935 5 0 6 1 2198.9138 4 0 5 1 (2199.035)* 3 0 4 1 (2199.158) 2 0 3 1 2199.2781 1 0 2 1 2199.4013 0 0 1 1 2199.5243 4 0 4 1 2199.6442* 3 1 4 0 2199.7627 2 1 3 0 2199.8888 (broad ~0.010) 3 0 2 1 2200.0116 4 0 3 1 2200.1350 4 1 4 0 2200.2526* 1 1 0 0 2200.3776 2 1 1 0 (2200.498) 3 1 2 0 2200.6207 4 1 3 0 2200.7430 4 2 4 1 2200.8602* 6 1 5 0 2200.9864 2 2 1 1 2201.1070 3 2 2 1 2201.2290 4 2 3 1 2201.3509 5 2 4 1 (2201.471)* 6 2 5 1 2201.5938 7 2 6 1 2201.7149 3 3 2 2 2201.8366 4 3 3 2 2201.9583 5 4 5 3 2202.0736* 5 3 4 2 2202.0784** 6 3 5 2 2202.2009 7 3 6 2 2202.3218 8 3 7 2 (2202.444) 4 4 3 3 2202.5644 8 3 7 2 (2202.444) 5 4 4 3 2202.6861* 6 4 5 3 2202.8073 7 4 6 3 2202.9289 8 4 7 3 2203.0503 9 4 8 3 (2203.172) 5 5 4 4 2203.2913* 6 5 5 4 2203.4131 ************************************************