  (abridged) We present high angular resolution (~ 1") multi-tracer spectral
line observations toward the hot core associated with G34.26+0.15 between
87--109 GHz. We have mapped emission from (i) complex nitrogen- and oxygen-rich
molecules like CH3OH, HC3N, C2H5CN, NH2CHO, CH3OCH3, HCOOCH3; (ii)
sulfur-bearing molecules like OCS, SO and SO2; and (iii) the recombination line
H53 beta. The high angular resolution enables us to directly probe the hot
molecular core associated with G34.26+0.15 at spatial scales of 0.018 pc. At
this resolution we find no evidence for the hot core being internally heated.
The continuum peak detected at lambda=2.8 mm is consistent with the free-free
emission from component C of the ultracompact H II region. Velocity structure
and morphology outlined by the different tracers suggest that the hot core is
primarily energized by component C. Emission from the N- and O-bearing
molecules peak at different positions within the innermost regions of the core;
none is coincident with the continuum peak. Based on the brightness
temperatures of optically thick lines in our sample, we estimate the kinetic
temperature of the inner regions of the HMC to be 160+-30 K. Comparison of the
observed abundances of the different species in G34.26+0.15 with existing
models does not produce a consistent picture.
