\begin{table}%t3 \caption{\label{t:detectetocho-a}Transitions of the \textit{anti}-conformer of ethyl formate detected toward Sgr~B2(N) with the IRAM 30~m telescope.} \small%\centerline { \begin{tabular}{rlrrrrrcrrrrl} \hline\hline \multicolumn{1}{c}{$N^a$} & \multicolumn{1}{c}{\hspace*{-1ex} Transition} & \multicolumn{1}{c}{\hspace*{-2ex} Frequency} & \multicolumn{1}{c}{\hspace*{-3ex} Unc.$^b$} & \multicolumn{1}{c}{\hspace*{-1ex} $E_{\rm l}$$^c$} & \multicolumn{1}{c}{\hspace*{-1ex} $S\mu^2$} & \multicolumn{1}{c}{\hspace*{-2ex} $\sigma^d$} & \multicolumn{1}{c}{$F^e$} & \multicolumn{1}{c}{$\tau^f$} & \multicolumn{1}{c}{$I_{{\rm obs}}$$^g$} & \multicolumn{1}{c}{\hspace*{-1ex} $I_{{\rm mod}}$$^g$} & \multicolumn{1}{c}{\hspace*{-1ex} $I_{{\rm all}}$$^g$} & \multicolumn{1}{c}{Comments} \\ & & \multicolumn{1}{c}{\hspace*{-2ex} \scriptsize (MHz)} & \multicolumn{1}{c}{\hspace*{-3ex} \scriptsize (kHz)} & \multicolumn{1}{c}{\hspace*{-1ex} \scriptsize (K)} & \multicolumn{1}{c}{\hspace*{-1ex} \scriptsize (D$^2$)} & \multicolumn{1}{c}{\hspace*{-2ex} \scriptsize (mK)} & & & \multicolumn{1}{c}{\scriptsize (K~km~s$^{-1}$)} & \multicolumn{2}{c}{\hspace*{-1ex} \scriptsize (K~km~s$^{-1}$)} & \\ \multicolumn{1}{c}{(1)} & \multicolumn{1}{c}{\hspace*{-1ex} (2)} & \multicolumn{1}{c}{\hspace*{-2ex} (3)} & \multicolumn{1}{c}{\hspace*{-3ex} (4)} & \multicolumn{1}{c}{\hspace*{-1ex} (5)} & \multicolumn{1}{c}{\hspace*{-1ex} (6)} & \multicolumn{1}{c}{\hspace*{-2ex} (7)} & \multicolumn{1}{c}{(8)} & \multicolumn{1}{c}{(9)} & \multicolumn{1}{c}{(10)} & \multicolumn{1}{c}{(11)} & \multicolumn{1}{c}{\hspace*{-1ex} (12)} & \multicolumn{1}{c}{\hspace*{-1ex} (13)} \\ \hline 1 & \hspace*{-1ex} 15$_{ 2,14}$--14$_{ 2,13}$ & \hspace*{-2ex} 81~779.567 & \hspace*{-3ex} 4 & \hspace*{-1ex} 30 & \hspace*{-1ex} 51 & \hspace*{-2ex} 13 & 1 & 0.05 & 0.52(06) & \hspace*{-2ex} 0.32 & \hspace*{-2ex} 0.44 & blend with $U$-line \\ 16 & \hspace*{-1ex} 15$_{ 6,10}$--14$_{ 6, 9}$ & \hspace*{-2ex} 82~351.854 & \hspace*{-3ex} 4 & \hspace*{-1ex} 54 & \hspace*{-1ex} 43 & \hspace*{-2ex} 19 & 2 & 0.07 & 1.02(08) & \hspace*{-2ex} 0.44 & \hspace*{-2ex} 0.55 & partial blend with C$_2$H$_5$CN, \\ & & & & & & & & & & & & $\varv_{13}$ = 1/$\varv_{21}$ = 1 and $U$-line \\ 17 & \hspace*{-1ex} 15$_{ 6, 9}$--14$_{ 6, 8}$ & \hspace*{-2ex} 82~351.858 & \hspace*{-3ex} 4 & \hspace*{-1ex} 54 & \hspace*{-1ex} 43 & \hspace*{-2ex} 19 & 2 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 26 & \hspace*{-1ex} 15$_{ 2,13}$--14$_{ 2,12}$ & \hspace*{-2ex} 84~081.357 & \hspace*{-3ex} 4 & \hspace*{-1ex} 31 & \hspace*{-1ex} 51 & \hspace*{-2ex} 19 & 3 & 0.05 & 0.53(08) & \hspace*{-2ex} 0.35 & \hspace*{-2ex} 0.42 & partial blend with CH$_3$CH$_3$CO, $\varv_t$ = 1 \\ 28 & \hspace*{-1ex} 16$_{ 0,16}$--15$_{ 0,15}$ & \hspace*{-2ex} 85~065.106 & \hspace*{-3ex} 4 & \hspace*{-1ex} 31 & \hspace*{-1ex} 55 & \hspace*{-2ex} 22 & 4 & 0.06 & 0.73(10) & \hspace*{-2ex} 0.39 & \hspace*{-2ex} 0.57 & partial blend with c-C$_2$H$_4$O \\ 44 & \hspace*{-1ex} 16$_{ 8, 8}$--15$_{ 8, 7}$ & \hspace*{-2ex} 87~810.372 & \hspace*{-3ex} 4 & \hspace*{-1ex} 78 & \hspace*{-1ex} 41 & \hspace*{-2ex} 17 & 5 & 0.05 & 1.28(07) & \hspace*{-2ex} 0.40 & \hspace*{-2ex} 1.22 & partial blend with CH$_2$(OH)CHO \\ & & & & & & & & & & & & and C$_2$H$_5$CN \\ 45 & \hspace*{-1ex} 16$_{ 8, 9}$--15$_{ 8, 8}$ & \hspace*{-2ex} 87~810.372 & \hspace*{-3ex} 4 & \hspace*{-1ex} 78 & \hspace*{-1ex} 41 & \hspace*{-2ex} 17 & 5 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 46 & \hspace*{-1ex} 16$_{ 7, 9}$--15$_{ 7, 8}$ & \hspace*{-2ex} 87~826.665 & \hspace*{-3ex} 4 & \hspace*{-1ex} 67 & \hspace*{-1ex} 44 & \hspace*{-2ex} 17 & 6 & 0.06 & 0.99(07) & \hspace*{-2ex} 0.48 & \hspace*{-2ex} 0.86 & partial blend with HNCO, $\varv_5$ = 1 \\ 47 & \hspace*{-1ex} 16$_{ 7,10}$--15$_{ 7, 9}$ & \hspace*{-2ex} 87~826.665 & \hspace*{-3ex} 4 & \hspace*{-1ex} 67 & \hspace*{-1ex} 44 & \hspace*{-2ex} 17 & 6 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 53 & \hspace*{-1ex} 16$_{ 3,14}$--15$_{ 3,13}$ & \hspace*{-2ex} 87~993.944 & \hspace*{-3ex} 4 & \hspace*{-1ex} 38 & \hspace*{-1ex} 53 & \hspace*{-2ex} 19 & 7 & 0.05 & 1.01(08) & \hspace*{-2ex} 0.39 & \hspace*{-2ex} 0.64 & partial blend with CH$_3$CH$_3$CO \\ & & & & & & & & & & & & and $U$-line \\ 54 & \hspace*{-1ex} 16$_{ 4,12}$--15$_{ 4,11}$ & \hspace*{-2ex} 88~001.562 & \hspace*{-3ex} 4 & \hspace*{-1ex} 43 & \hspace*{-1ex} 51 & \hspace*{-2ex} 19 & 8 & 0.05 & 0.66(08) & \hspace*{-2ex} 0.35 & \hspace*{-2ex} 0.62 & blend with C$_2$H$_5$CN, $\varv_{13}$ = 1/$\varv_{21}$ = 1 \\ 73 & \hspace*{-1ex} 17$_{10, 7}$--16$_{10, 6}$ & \hspace*{-2ex} 93~284.077 & \hspace*{-3ex} 4 & \hspace*{-1ex} 108 & \hspace*{-1ex} 38 & \hspace*{-2ex} 22 & 9 & 0.04 & 0.07(09) & \hspace*{-2ex} 0.33 & \hspace*{-2ex} 0.35 & uncertain baseline \\ 74 & \hspace*{-1ex} 17$_{10, 8}$--16$_{10, 7}$ & \hspace*{-2ex} 93~284.077 & \hspace*{-3ex} 4 & \hspace*{-1ex} 108 & \hspace*{-1ex} 38 & \hspace*{-2ex} 22 & 9 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 75 & \hspace*{-1ex} 17$_{ 9, 8}$--16$_{ 9, 7}$ & \hspace*{-2ex} 93~292.297 & \hspace*{-3ex} 4 & \hspace*{-1ex} 94 & \hspace*{-1ex} 42 & \hspace*{-2ex} 22 & 10 & 0.05 & 0.56(09) & \hspace*{-2ex} 0.42 & \hspace*{-2ex} 0.50 & uncertain baseline \\ 76 & \hspace*{-1ex} 17$_{ 9, 9}$--16$_{ 9, 8}$ & \hspace*{-2ex} 93~292.297 & \hspace*{-3ex} 4 & \hspace*{-1ex} 94 & \hspace*{-1ex} 42 & \hspace*{-2ex} 22 & 10 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 77 & \hspace*{-1ex} 17$_{ 8, 9}$--16$_{ 8, 8}$ & \hspace*{-2ex} 93~304.955 & \hspace*{-3ex} 4 & \hspace*{-1ex} 82 & \hspace*{-1ex} 45 & \hspace*{-2ex} 22 & 11 & 0.06 & 0.96(09) & \hspace*{-2ex} 0.51 & \hspace*{-2ex} 0.67 & partial blend with $U$-line \\ 78 & \hspace*{-1ex} 17$_{ 8,10}$--16$_{ 8, 9}$ & \hspace*{-2ex} 93~304.955 & \hspace*{-3ex} 4 & \hspace*{-1ex} 82 & \hspace*{-1ex} 45 & \hspace*{-2ex} 22 & 11 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 79 & \hspace*{-1ex} 17$_{ 7,11}$--16$_{ 7,10}$ & \hspace*{-2ex} 93~324.728 & \hspace*{-3ex} 4 & \hspace*{-1ex} 71 & \hspace*{-1ex} 48 & \hspace*{-2ex} 22 & 12 & 0.07 & 1.32(09) & \hspace*{-2ex} 0.60 & \hspace*{-2ex} 0.74 & partial blend with $U$-lines \\ 80 & \hspace*{-1ex} 17$_{ 7,10}$--16$_{ 7, 9}$ & \hspace*{-2ex} 93~324.728 & \hspace*{-3ex} 4 & \hspace*{-1ex} 71 & \hspace*{-1ex} 48 & \hspace*{-2ex} 22 & 12 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 81 & \hspace*{-1ex} 17$_{ 6,12}$--16$_{ 6,11}$ & \hspace*{-2ex} 93~356.821 & \hspace*{-3ex} 4 & \hspace*{-1ex} 62 & \hspace*{-1ex} 51 & \hspace*{-2ex} 22 & 13 & 0.08 & 1.68(10) & \hspace*{-2ex} 0.70 & \hspace*{-2ex} 1.24 & blend with CH$_3$CH$_3$CO and $U$-line? \\ 82 & \hspace*{-1ex} 17$_{ 6,11}$--16$_{ 6,10}$ & \hspace*{-2ex} 93~356.838 & \hspace*{-3ex} 4 & \hspace*{-1ex} 62 & \hspace*{-1ex} 51 & \hspace*{-2ex} 22 & 13 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 83 & \hspace*{-1ex} 17$_{ 5,13}$--16$_{ 5,12}$ & \hspace*{-2ex} 93~412.160 & \hspace*{-3ex} 4 & \hspace*{-1ex} 54 & \hspace*{-1ex} 53 & \hspace*{-2ex} 22 & 14 & 0.08 & 1.12(10) & \hspace*{-2ex} 0.79 & \hspace*{-2ex} 0.85 & partial blend with $U$-line? \\ 84 & \hspace*{-1ex} 17$_{ 5,12}$--16$_{ 5,11}$ & \hspace*{-2ex} 93~413.168 & \hspace*{-3ex} 4 & \hspace*{-1ex} 54 & \hspace*{-1ex} 53 & \hspace*{-2ex} 22 & 14 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 86 & \hspace*{-1ex} 17$_{ 4,14}$--16$_{ 4,13}$ & \hspace*{-2ex} 93~504.972 & \hspace*{-3ex} 4 & \hspace*{-1ex} 47 & \hspace*{-1ex} 55 & \hspace*{-2ex} 24 & 15 & 0.05 & 1.47(10) & \hspace*{-2ex} 0.44 & \hspace*{-2ex} 0.87 & blend with CH$_3$$^{18}$OH \\ 87 & \hspace*{-1ex} 17$_{ 4,13}$--16$_{ 4,12}$ & \hspace*{-2ex} 93~539.303 & \hspace*{-3ex} 4 & \hspace*{-1ex} 47 & \hspace*{-1ex} 55 & \hspace*{-2ex} 24 & 16 & 0.05 & 0.84(10) & \hspace*{-2ex} 0.44 & \hspace*{-2ex} 0.45 & no blend \\ 94 & \hspace*{-1ex} 18$_{15, 3}$--17$_{15, 2}$ & \hspace*{-2ex} 98~760.931 & \hspace*{-3ex} 5 & \hspace*{-1ex} 202 & \hspace*{-1ex} 19 & \hspace*{-2ex} 18 & 17 & 0.04 & 0.87(09) & \hspace*{-2ex} 0.68 & \hspace*{-2ex} 0.78 & blend with $U$-line \\ 95 & \hspace*{-1ex} 18$_{15, 4}$--17$_{15, 3}$ & \hspace*{-2ex} 98~760.931 & \hspace*{-3ex} 5 & \hspace*{-1ex} 202 & \hspace*{-1ex} 19 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 96 & \hspace*{-1ex} 18$_{14, 4}$--17$_{14, 3}$ & \hspace*{-2ex} 98~761.079 & \hspace*{-3ex} 5 & \hspace*{-1ex} 181 & \hspace*{-1ex} 24 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 97 & \hspace*{-1ex} 18$_{14, 5}$--17$_{14, 4}$ & \hspace*{-2ex} 98~761.079 & \hspace*{-3ex} 5 & \hspace*{-1ex} 181 & \hspace*{-1ex} 24 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 98 & \hspace*{-1ex} 18$_{16, 2}$--17$_{16, 1}$ & \hspace*{-2ex} 98~761.555 & \hspace*{-3ex} 5 & \hspace*{-1ex} 224 & \hspace*{-1ex} 13 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 99 & \hspace*{-1ex} 18$_{16, 3}$--17$_{16, 2}$ & \hspace*{-2ex} 98~761.555 & \hspace*{-3ex} 5 & \hspace*{-1ex} 224 & \hspace*{-1ex} 13 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 100 & \hspace*{-1ex} 18$_{13, 5}$--17$_{13, 4}$ & \hspace*{-2ex} 98~762.218 & \hspace*{-3ex} 5 & \hspace*{-1ex} 162 & \hspace*{-1ex} 30 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 101 & \hspace*{-1ex} 18$_{13, 6}$--17$_{13, 5}$ & \hspace*{-2ex} 98~762.218 & \hspace*{-3ex} 5 & \hspace*{-1ex} 162 & \hspace*{-1ex} 30 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 102 & \hspace*{-1ex} 18$_{17, 1}$--17$_{17, 0}$ & \hspace*{-2ex} 98~762.790 & \hspace*{-3ex} 5 & \hspace*{-1ex} 248 & \hspace*{-1ex} 7 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 103 & \hspace*{-1ex} 18$_{17, 2}$--17$_{17, 1}$ & \hspace*{-2ex} 98~762.790 & \hspace*{-3ex} 5 & \hspace*{-1ex} 248 & \hspace*{-1ex} 7 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 104 & \hspace*{-1ex} 18$_{12, 6}$--17$_{12, 5}$ & \hspace*{-2ex} 98~764.650 & \hspace*{-3ex} 5 & \hspace*{-1ex} 144 & \hspace*{-1ex} 34 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 105 & \hspace*{-1ex} 18$_{12, 7}$--17$_{12, 6}$ & \hspace*{-2ex} 98~764.650 & \hspace*{-3ex} 5 & \hspace*{-1ex} 144 & \hspace*{-1ex} 34 & \hspace*{-2ex} 18 & 17 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 118 & \hspace*{-1ex} 18$_{ 5,14}$--17$_{ 5,13}$ & \hspace*{-2ex} 98~928.453 & \hspace*{-3ex} 4 & \hspace*{-1ex} 58 & \hspace*{-1ex} 57 & \hspace*{-2ex} 18 & 18 & 0.07 & 2.37(09) & \hspace*{-2ex} 0.96 & \hspace*{-2ex} 2.23 & blend with C$_2$H$_5$CN, $\varv_{13}$ = 1/$\varv_{21}$ = 1 \\ 119 & \hspace*{-1ex} 18$_{ 5,13}$--17$_{ 5,12}$ & \hspace*{-2ex} 98~930.153 & \hspace*{-3ex} 4 & \hspace*{-1ex} 58 & \hspace*{-1ex} 57 & \hspace*{-2ex} 18 & 18 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 160 & \hspace*{-1ex} 20$_{ 1,20}$--19$_{ 1,19}$ & \hspace*{-2ex} 105~234.713 & \hspace*{-3ex} 5 & \hspace*{-1ex} 49 & \hspace*{-1ex} 68 & \hspace*{-2ex} 28 & 19 & 0.07 & 1.66(11) & \hspace*{-2ex} 0.76 & \hspace*{-2ex} 1.27 & blend with C$_2$H$_5$OH and CH$_3$OCHO \\ 161 & \hspace*{-1ex} 19$_{ 1,18}$--18$_{ 1,17}$ & \hspace*{-2ex} 105~272.047 & \hspace*{-3ex} 5 & \hspace*{-1ex} 47 & \hspace*{-1ex} 65 & \hspace*{-2ex} 28 & 20 & 0.07 & 2.07(11) & \hspace*{-2ex} 0.73 & \hspace*{-2ex} 0.81 & blend with $U$-lines \\ 162 & \hspace*{-1ex} 19$_{ 3,16}$--18$_{ 3,15}$ & \hspace*{-2ex} 105~447.141 & \hspace*{-3ex} 5 & \hspace*{-1ex} 52 & \hspace*{-1ex} 64 & \hspace*{-2ex} 37 & 21 & 0.06 & 1.07(15) & \hspace*{-2ex} 0.69 & \hspace*{-2ex} 1.07 & no blend \\ 165 & \hspace*{-1ex} 20$_{ 2,19}$--19$_{ 2,18}$ & \hspace*{-2ex} 108~552.378 & \hspace*{-3ex} 100 & \hspace*{-1ex} 53 & \hspace*{-1ex} 68 & \hspace*{-2ex} 20 & 22 & 0.07 & 2.05(08) & \hspace*{-2ex} 0.79 & \hspace*{-2ex} 1.24 & partial blend with C$_2$H$_3$CN, $\varv_{15}$ = 1 \\ & & & & & & & & & & & & and $U$-lines \\ 233 & \hspace*{-1ex} 21$_{ 6,16}$--20$_{ 6,15}$ & \hspace*{-2ex} 115~395.797 & \hspace*{-3ex} 5 & \hspace*{-1ex} 81 & \hspace*{-1ex} 66 & \hspace*{-2ex} 60 & 23 & 0.11 & 2.94(23) & \hspace*{-2ex} 1.37 & \hspace*{-2ex} 1.37 & partial blend with $U$-line \\ 234 & \hspace*{-1ex} 21$_{ 6,15}$--20$_{ 6,14}$ & \hspace*{-2ex} 115~395.986 & \hspace*{-3ex} 5 & \hspace*{-1ex} 81 & \hspace*{-1ex} 66 & \hspace*{-2ex} 60 & 23 & -- & -- & \hspace*{-2ex} -- & \hspace*{-2ex} -- & -- \\ 238 & \hspace*{-1ex} 22$_{ 1,22}$--21$_{ 1,21}$ & \hspace*{-2ex} 115~595.764 & \hspace*{-3ex} 5 & \hspace*{-1ex} 59 & \hspace*{-1ex} 75 & \hspace*{-2ex} 79 & 24 & 0.08 & --0.05(30) & \hspace*{-2ex} 0.99 & \hspace*{-2ex} 2.22 & blend with CH$_3$CH$_3$CO, $\varv_t$ = 1, \\ & & & & & & & & & & & & uncertain baseline \\ \hline \end{tabular}} \medskip Notes: $^a$ Numbering of the observed transitions associated with a modeled line stronger than 20~mK (see Table~\ref{t:etocho-a}). $^b$~Frequency uncertainty. $^c$~Lower energy level in temperature units ($E_{\rm l}/k_{\rm B}$). $^d$~Calculated rms noise level in $T_{{\rm mb}}$~scale. $^e$~Numbering of the observed features. $^f$~Peak opacity of the modeled feature. $^g$~Integrated intensity in $T_{{\rm mb}}$ scale for the observed spectrum (Col.~10), the ethyl formate model (Col.~11), and the model including all molecules (Col.~12). The uncertainty in Col.~10 is given in parentheses in units of the last digit. \end{table}