Detachment, an important mechanism for reducing target heat deposition, is achieved through reductions in power, particle and momentum; which are induced through plasma-atom and plasma-molecule interactions. Experimental research in how those reactions precisely contribute to detachment is limited. In this work, we investigate a new spectroscopic technique to utilise Hydrogen Balmer line measurements to 1) disentangle the Balmer line emission from the various plasma-atom and plasma-molecule interactions; and 2) quantify their contributions to ionisation, recombination and radiative power losses. During detachment, the observed $Halpha$ emission often strongly increases, which could be an indicator for plasma-molecule interactions involving $H_2^+$ and/or $H^-$. Our analysis technique quantifies the $Halpha$ emission due to plasma-molecule interactions and uses this to 1) quantify the Balmer line emission contribution due to $H_2^+$ and/or $H^-$; 2) subsequently estimate its resulting particle sinks/sources and radiative power losses. Its performance is verified using synthetic diagnostic techniques of both detached TCV and MAST-U SOLPS-ITER simulations. Experimental results of this technique on TCV data show a bifurcation occurs between the measured total $Halpha$ and the atomic estimate of $Halpha$ emission, indicative of the presence of additional $Halpha$ due to plasma-molecule interactions with $H_2^+$ (and/or $H^-$). An example analysis shows that the hydrogenic line series, even $Lyalpha$ as well as the medium-n Balmer lines can be significantly influenced by plasma-molecule interactions by tens of percent during which significant Molecular Activated Recombination (MAR) is expected.
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