Table 3.

Spectroscopic information (rest frequency, Einstein coefficients [$A_{\mathrm{u}\mathrm{l}}$], and energy of the upper levels [$E_{\mathrm{u}\mathrm{p}}$]) of the rotational transitions of ketenyl (HCCO) tentatively detected toward the G+0.693 molecular cloud (shown in Fig. 6)

Frequency, GHz	Transition	log$A_{\mathrm{u}\mathrm{l}}$, ${\mathrm{s}}^{-1}$	$E_{\mathrm{u}\mathrm{p}}$, K
43.3176674	2(3,3)–1(2,2)	−6.0192	3.1
43.3211451	2(3,2)–1(2,1)	−6.1404	3.1
43.3295421	2(2,2)–1(1,1)	−6.0343	3.1
43.3354627	2(2,1)–1(1,0)	−6.2739	3.1
43.3368615	2(3,2)–1(2,2)	−6.6741	3.1
43.3373040	2(2,1)–1(2,1)	−6.4207	3.1
86.6191857	4(4,3)–3(3,3)	−6.9202	10.4
86.6423419	4(5,5)–3(4,4)	−5.0703	10.4
86.6438483	4(5,4)–3(4,3)	−5.0942	10.4
86.6558306	4(4,4)–3(3,3)	−5.0772	10.4
86.6574849	4(4,3)–3(3,2)	−5.1070	10.4
86.6652791	4(5,4)–3(4,4)	−6.3845	10.4
108.2823800	5(5,4)–4(4,4)	−6.7293	15.6
108.3040553	5(6,6)–4(5,5)	−4.7698	15.6
108.3051187	5(6,5)–4(5,4)	−4.7840	15.6
108.3178903	5(5,5)–4(4,4)	−4.7747	15.6
108.3190248	5(5,4)–4(4,3)	−4.7916	15.6
108.3280559	5(6,5)–4(5,5)	−6.2997	15.6