\begin{table}%t2
\caption{\label{tab:fitparameter}Spectroscopic parameters for DME in the vibrational
  ground state.  }

\par
%\centerline
{
\small$$\begin{tabular}{lr@{.}lr@{.}l}
  \hline \hline
  Parameter$^a$ & \multicolumn{2}{c}{This work} &
  \multicolumn{2}{c}{\citet{Groner1998}} \\ \hline
  $\rho$                    &     0&217131(37)       &     0&21709(21)      \\
  $\beta$ (deg)             &     9&117(17)          &     8&631(13)        \\ \hline
  $A$ (MHz)                 & 38788&18325(28)        & 38788&17932(71)      \\
  $B$ (MHz)                 & 10056&482389(77)       & 10056&48166(18)      \\
  $C$ (MHz)                 &  8886&829843(75)       &  8886&82907(19)      \\
  $\varDelta_J$ (kHz)       &     9&085900(59)       &     9&08387(36)      \\
  $\varDelta_{JK}$ (kHz)    & $-$26&86387(64)        & $-$26&8656(39)       \\
  $\varDelta_K$ (kHz)       &   341&9520(17)         &   341&721(41)        \\
  $\delta_J$ (kHz)          &     1&775148(25)       &     1&775099(53)     \\
  $\delta_K$ (kHz)          & $-$13&8034(12)         & $-$13&7825(44)       \\
  $\varPhi_J$ (Hz)          &     0&007798(12)       &     0&00703(19)      \\
  $\varPhi_{JK}$ (Hz)       &     0&1122(28)         &     0&1121(67)       \\
  $\varPhi_{KJ}$ (Hz)       &  $-$4&0865(90)         &  $-$3&847(88)        \\
  $\varPhi_K$ (Hz)          &    13&7300(72)         &     8&38(107)        \\
  $\phi_J$ (Hz)             &     0&003796(16)       &     0&003745(43)     \\
  $\phi_{JK}$ (Hz)          &     0&31571(57)        &     0&3341(57)       \\
  $\phi_K$ (Hz)             &     1&010(91)          &     1&50(22)         \\
  $L_{JJK}$ (mHz)           &     0&00687(95)        & \multicolumn{2}{c}{} \\
  $L_{JK}$  (mHz)           &     0&3079(35)         & \multicolumn{2}{c}{} \\
  $L_{JKK}$ (mHz)           &  $-$0&7941(54)         & \multicolumn{2}{c}{} \\
  $l_J$     (mHz)           &     0&0000260(30)      & \multicolumn{2}{c}{} \\
  $l_{JKK}$ (mHz)           &     0&290(31)          & \multicolumn{2}{c}{} \\
  $l_K$     (mHz)           &     6&671(37)          & \multicolumn{2}{c}{} \\ \hline
  Tunneling parameters$^b$  & \multicolumn{2}{c}{}   & \multicolumn{2}{c}{} \\ \hline
  $\epsilon_{10}$ (MHz)     &  $-$3&0445(11)         &  $-$3&0435(41)      \\
  $\epsilon_{20}$ (MHz)     & \multicolumn{2}{c}{}   &     0&0053(16)      \\
  $[A-(B+C)/2]_{10}$ (kHz)  &     2&149(36)          &     1&64(21)        \\
  $[(B+C)/2]_{10}$ (kHz)    &  $-$0&416(11)          &  $-$0&0364(63)      \\
  $[(B-C)/4]_{10}$ (kHz)    &  $-$0&0908(92)         &     0&1116(37)   \\
  $[\varDelta_J]_{10}$ (Hz)    &  0&2209(48)         & \multicolumn{2}{c}{} \\
  $[\varDelta_{JK}]_{10}$ (Hz) &$-$1&797(36)         & \multicolumn{2}{c}{} \\
  $[\varDelta_K]_{10}$ (Hz)    &   1&74(16)          & \multicolumn{2}{c}{} \\
  $[\delta_J]_{10}$ (Hz)    &      0&1579(82)        & \multicolumn{2}{c}{} \\
  $[\delta_K]_{10}$ (Hz)    &      1&099(64)         & \multicolumn{2}{c}{} \\
  $[\phi_J]_{10}$ (mHz)     &   $-$0&0432(16)        & \multicolumn{2}{c}{} \\
  $[\phi_K]_{10}$ (mHz)     &   $-$2&29(22)          & \multicolumn{2}{c}{} \\\hline
\end{tabular}$$}
\par
\medskip
$^a$ The non-tunneling parameters $T_{l \quad 00}^{(\kappa)}$ are
    labeled using the common notation for rotational constants.
    \\
    $^b$ For tunneling parameters the notation $[\quad]_{qq'}$ has been used with the
    commonly used notation of corresponding non-tunneling parameters
    enclosed by the brackets.
\end{table}