ExoMol line list XXXIV: A Rovibrational Line List for Phosphinidene (PH) in its $X\,{}^3Σ^-$ and $a\,{}^1Δ$ Electronic States

A rovibronic line list for the ground ($X$ $^3Σ^-$) and first excited ($a$ $^1Δ$) states of phosphinidene, $^{31}$PH, is computed. The line list is designed for studies of exoplanetary and cool stellar atmospheres with temperatures up to 4000 K. A combination of empirical and ab initio data are used to produce the line list: potential energy curves (PECs) are fitted using experimental transition frequencies; these transitions are reproduced with a root mean square error of 0.01 cm$^{-1}$. The nuclear Schrödinger is solved using these PECs plus Born-Oppenheimer and spin splitting correction terms. Line intensities and Einstein $A$ coefficients are computed using ab initio Dipole Moment Curves (DMC) $X$-$X$ and $a$-$a$. The resulting LaTY line list, which contains 65055 transitions for 2528 rovibronic states up to 24500 cm$^{-1}$ and $J=80$ is used to simulate spectra in emission and absorption at a range of temperatures. The line list is made available in electronic form at the CDS and ExoMol databases.