  Binding energies of negative ($X^-$) and positive trions ($X^+$) in quantum
wires are studied for strong quantum confinement of carriers which results in a
numerical exactly solvable model. The relative electron and hole localization
has a strong effect on the stability of trions. For equal hole and electron
confinement, $X^+$ is more stable but a small imbalance of the particle
localization towards a stronger hole localization e.g. due to its larger
effective mass, leads to the interchange of $X^-$ and $X^+$ recombination lines
in the photoluminescent spectrum as was recently observed experimentally. In
case of larger $X^-$ stability, a magnetic field oriented parallel to the wire
axis leads to a stronger increase of the $X^+$ binding energy resulting in a
crossing of the $X^+$ and $X^-$ lines.

Mesoscale and Nanoscale Physics