Investigating the Minimum Energy Principle in Searches for New Molecular
  Species - the Case of H$_{2}$C$_{3}$O Isomers
  Recently, Lattelais et al. (2009) have interpreted aggregated observations of
molecular isomers to suggest that there exists a "minimum energy principle'',
such that molecular formation will favor more stable molecular isomers for
thermodynamic reasons. To test the predictive power of this principle, we have
fully characterized the spectra of the three isomers of C$_{3}$H$_{2}$O toward
the well known molecular region Sgr B2(N). Evidence for the detection of the
isomers cyclopropenone (c-C$_{3}$H$_{2}$O) and propynal (HCCCHO) is presented,
along with evidence for the non-detection of the lowest zero-point energy
isomer, propadienone (CH$_2$CCO). We interpret these observations as evidence
that chemical formation pathways, which may be under kinetic control, have a
more pronounced effect on final isomer abundances than thermodynamic effects
such as the minimum energy principle.
