File Name : figure s1.tiff

Caption : (a) an example of a mass spectrum recorded when the discharge was turned off. (b) the corresponding mass spectrum obtained when the discharge was turned on. (c) the difference spectrum obtained by subtracting (b) from (a). 

File Name : figure s2.tiff

Caption : histogram plot of the distribution of cross section values and associated errors. the distribution is fitted with a gaussian function to give a mean value for the ionization cross section as 14.3 ± 4.8 mb. 

File Name : figure s3 left.tiff

Caption : simulations of the tpes of sh. the left panel displays a simulation with a vibrational population corresponding to t<sub>vib</sub> = 1900 k (t<sub>spin</sub> = 0.001 k). the middle panel shows a simulation that populates the ω = ½ spin-orbit component of the sh ground state using t<sub>spin</sub> = 120 k (t<sub>vib</sub> = 0.001 k). the simulation is more satisfactory than the previous one which did not populate the ω = ½ component. a slightly better agreement is obtained in the right panel which was obtained by using t<sub>spin</sub> = 100 k & t<sub>vib</sub> = 1500 k.