THE OPTICAL SPECTRUM OF SrOH RE-VISITED: ZEEMAN EFFECT, HIGH-RESOLUTION SPECTROSCOPY AND FRANCK-CONDON FACTORS.

Motivated by a diverse range of applications in physics and chemistry, currently there is great interest in the cooling of molecules to very low temperatures ($leq$1,mK). Direct laser cooling has been previously demonstrated for the diatomic radicals SrFfootnote{E.S. Shuman, J.F. Barry and D. DeMille, Nature 467, 820 (2010)}$^,$footnote{J.F. Barry, E.S. Shuman, E.B. Norrgard and D. DeMille, Phys. Rev. Lett. 108, 103002 (2012)}, YOfootnote{M.T. Hummon, M. Yeo, B.K. Stuhl, A.L. Collopy, Y. Xia, and J. Ye, Phys. Rev. Lett. 110, 143001 (2013)}$^,$footnote{M. Yeo, M.T. Hummon, A.L. Collopy, B. Yan, B. Hemmerling, E. Chae, J.M. Doyle, and J. Ye, arXiv:1501.04683 (2015)}, and CaFfootnote{V. Zhelyazkova, A. Cournol, T.E. Wall, A. Matsushima, J.J. Hudson, E.A. Hinds, M.R. Tarbutt, and B.E. Sauer, Phys. Rev. A 89, 053416 (2014)}, and most recently a three-dimensional magneto-optical trap (MOT) of SrF molecules was achievedfootnote{J.F. Barry, D.J. McCarron, E.B. Norrgard, M.H. Steinecker and D. DeMille, Nature 512, 286 (2014)}$^,$footnote{D.J. McCarron, E.B. Norrgard, M.H. Steinecker and D. DeMille, arXiv:1412.8220 (2014)}. To determine the possibility of laser cooling for polyatomic molecules containing three or more atoms, detailed information is required about their Franck-Condon factors (FCFs) for emission from the excited states of interest. Here we report on the high-resolution laser excitation spectra, recorded field-free and in the presence of a static magnetic field, and on the dispersed fluorescence (DF) spectra for the $A^2Pi_{1/2} leftarrow X^2Sigma^+$ and $B^2Sigma^+ leftarrow X ^2Sigma^+$ electronic transitions of SrOH. The DF spectra were analyzed to precisely determine FCFs and compared with values predicted using a normal coordinate GF matrix approach. The recorded Zeeman spectra were analyzed to determine the magnetic moments. Implication for proposed laser cooling and trapping experiments for SrOH will be presented