  Context: High-resolution spectra in the near-infrared (NIR) are an important
tool for the detailed study of stellar atmospheres. The accurate identification
of elements and molecules in these spectra can be used to determine chemical
abundances and physical conditions in the photosphere of the observed star.
Such identifications require precise line positions and strengths of both
atomic and molecular features. Aims: This work focusses on the full
identification of absorption lines in the NIR spectrum of the K-giant 10 Leo,
including previously unidentified lines. The large number and complexity of the
observed absorption lines require a deep search for potential spectral
signatures to enable an unambiguous assignment to specific elements or
molecular species. We aim to improve the published line lists of metals, some
of which are determined by model calculations only, and many of which presently
lack the completeness and accuracy of line parameters. Methods: The CRIRES-POP
project provided high-resolution, high signal-to-noise ratio (S/N) spectra of
several bright stars in the 1 to 5 $\mu$m range. For the K-giant 10 Leo, a
spectrum corrected for telluric absorption and with precise wavelength
calibration is available. This has been analysed by comparison with model
spectra and up-to-date line lists. Results: We identified lines of 29 elements
and eight molecular species. While the positions of many known lines could be
confirmed, about 6% of all lines detected in 10 Leo could not be attributed to
any known feature. For CO and its isotopologues, molecular constants could be
derived and several additional lines identified. We report major
inconsistencies for some prominent lines. In addition, abundances for several
key elements in 10 Leo are provided.
