\begin{table}%t8
\caption{\label{Table: required Tbg for TA 10mK}Estimated required background temperatures to produce absorption lines with \mbox{$T_{\rm b}=-10$~mK}  at an observing frequency of~550~GHz assuming  \mbox{$T_{\rm ex} \ll T_{\rm bg}$}, and an opacity of one or~10$^{-3}$.} 
%\centering
\par
\begin{tabular}{lccrr}
\hline \hline \noalign{\smallskip}
Transition & Redshift  & Opacity &  	$T_{\rm bg}$  &  $T_{\rm CMB}$\\ 
  & $z$   & $\tau$ & [K]& [K]\\   
\hline
H$_2$(2--0)	&	18.3		&	1			&	58	&	53\\  
		&			&	10$^{-3}$	&	260 \\   
H$_2$(3--1)	& 	31.0		&	1			&	96		& 87\\  
	&			&	10$^{-3}$	&	430 \\ 
H$_2$(4--2)	& 	43.4		&	1			&	132	&	121	\\ 
	&			&	10$^{-3}$	&	595 \\
H$_2$(5--3)	& 	 55.4	&	1			&	168		& 154 \\ 
	&			&	10$^{-3}$	&	756 \\			
 HD(4--3)		&	18.1		&	1			&	57	&	52	\\  
        &			&	10$^{-3}$	&	257 \\   
\par
HD(5--4)		&	22.7		&	1			&	71		&	65 \\  
        &			&	10$^{-3}$	&	317 \\    
HeH$^+$(4--3)	&	13.4		&	1			&	 43	&	39	\\  
        &			&	10$^{-3}$	&	  194&	 	\\    
HeH$^+$(5--4)	&	16.7		&	1			&	 54	&	48\\  
        &			&	10$^{-3}$	&	240	&  \\  
\hline
\end{tabular}
\tablefoot {Note, that since the observing frequencies are the same for all transitions the source redshift is different for every transition. As~a comparison, the CMB~temperatures are listed for each redshift.}
\end{table}