ALMA Detection of Vibrationally Excited ($v\mathrm{_t} = 1,2$) Acetic
  Acid toward NGC 6334I
  Vibrationally excited states of detected interstellar molecules have been
shown to account for a large portion of unidentified spectral lines in observed
interstellar spectra toward chemically rich sources. Here, we present the first
interstellar detection of the first and second vibrationally excited torsional
states of acetic acid ($v_\mathrm{t} = 1, 2$) toward the high-mass star-forming
region NGC 6334I. The observations presented were taken with the Atacama Large
Millimeter/submillimeter Array in bands 4, 6, and 7 covering a frequency range
of 130 - 352 GHz. By comparing a single excitation temperature model to the
observations, the best-fit excitation temperature and column density are
obtained to be 142(25) K and $1.12(7) \times 10^{17} \mathrm{cm^{-2}}$
respectively. Based on the intensity maps of the vibrationally excited
CH$_3$COOH transitions, we found that the CH$_3$COOH emissions are compact and
concentrated toward the MM1 and MM2 regions with a source size smaller than 2
arcsec. After locating the emission from different CH$_3$COOH transitions,
which cover a large range of excitation energies, we are able to explain the
variation of the CH$_3$COOH emission peak within the MM2 core by invoking
continuum absorption or outflows.
