“…Some complexes have been studied spectroscopically in both the microwave and infrared regions, such as polar (N 2 O) 2 [1][2][3][4], polar (OCS) 2 [5,6], (OCS) 3 [7,8], (C 2 H 2 ) 2 [9,10], OCS-CO 2 [11,12], CO 2 -N 2 O [13][14][15], CO 2 -C 2 H 2 [16,17], and N 2 O-C 2 H 2 [18][19][20][21][22]. Others have been studied only by means of their infrared spectra, either because of their nonpolar structure like nonpolar (N 2 O) 2 [4,[23][24][25][26][27], nonpolar (OCS) 2 [28,29], and (CO 2 ) 2 [30,31], or because of complications arising from extensive hyperfine structure, like (N 2 O) 3 [32,33]. Still other complexes have hitherto been studied only by microwave spectroscopy, for example the subject of the present paper, OCS-C 2 H 2 , which occurs as two distinct isomers as shown by Peebles and Kuczkowski [34,35].…”