Searching for Trans Ethyl Methyl Ether in Orion KL
  We report on the tentative detection of $trans$ Ethyl Methyl Ether (tEME),
$t-CH_3CH_2OCH_3$, through the identification of a large number of rotational
lines from each one of the spin states of the molecule towards Orion KL. We
also search for $gauche$-$trans$-n-propanol, $Gt-n-CH_3CH_2CH_2OH$, an isomer
of tEME in the same source. We have identified lines of both species in the
IRAM 30m line survey and in the ALMA Science Verification data. We have
obtained ALMA maps to establish the spatial distribution of these species.
Whereas tEME mainly arises from the compact ridge component of Orion,
Gt-n-propanol appears at the emission peak of ethanol (south hot core). The
derived column densities of these species at the location of their emission
peaks are $\leq(4.0\pm0.8)\times10^{15} cm^{-2}$ and
$\leq(1.0\pm0.2)\times10^{15} cm^{-2}$ for tEME and Gt-n-propanol,
respectively. The rotational temperature is $\sim100 K$ for both molecules. We
also provide maps of $CH_3OCOH$, $CH_3CH_2OCOH$, $CH_3OCH_3$, $CH_3OH$, and
$CH_3CH_2OH$ to compare the distribution of these organic saturated O-bearing
species containing methyl and ethyl groups in this region. Abundance ratios of
related species and upper limits to the abundances of non-detected ethers are
provided. We derive an abundance ratio $N(CH_3OCH_3)/N(tEME)\geq150$ in the
compact ridge of Orion.
