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The laser induced fluorescence spectrum of phenyl-tetrazine ($C6H5-C2N4H$), its weakly bound dimer, and its van der Waals complex with argon were observed in a supersonic free jet. The 0-0 band of the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}B1\leftarrow 1A1(\pi \ast \leftarrow n)$ electronic transition of phenyl-tetrazine occurs at $17617.8cm-1$. Analysis of the rotational structure of phenyl-tetrazine indicated that the molecule was planar in both its ground and excited electronic states. Several van der Waals complexes of argon with phenyl-tetrazine were observed. Rotational analysis showed that the simplest argon van der Waals molecule, Ar-phenyl-tetrazine, has the argon atom out of plane above the center of the tetrazine ring at a distance of $3.34\backslash AA$. Two satellites of the 0-0 band at $-99cm-1$ and $+36cm-1$ were assigned to the dimer of phenyl-tetrazine. The two bands are produced by two different geometric isomers of the dimer.