= I. P. Clark
{c}
\b[I. P. Clark] coauthored the 2005 <spatially offset Raman spectroscopy> paper. Its collection geometry changes the mixture of signals arriving from an obscuring surface and the material below it.<Subsurface Probing in Diffusely Scattering Media Using Spatially Offset Raman Spectroscopy by P. Matousek and others>[exact byline and Abstract]{ref}
The Research Complex at Harwell identifies \b[Ian Clark] as an Ultra instrument scientist and describes his work on a <microbolometer> array for measuring the focal size of <infrared> beams. Knowing a beam's size matters when comparing excitation conditions in <time-resolved spectroscopy>.<Ian Clark by the Research Complex at Harwell>[researcher profile, infrared focal-spot measurement paragraph]{ref}
For an original <Gaussian beam> example, suppose the pulse <radiant exposure> is $F(r)=F_0\exp(-2r^2/w^2)$, with total pulse <energy> $E$. Integration over the transverse plane gives $E=F_0\pi w^2/2$, so $F_0=2E/(\pi w^2)$. If the actual radius is $110\,\mu\mathrm{m}$ but the analysis assumes $100\,\mu\mathrm{m}$, it overestimates peak <radiant exposure> by $(110/100)^2=1.21$, or $21\%$. Measuring pulse <energy> alone therefore does not determine the excitation delivered per unit area. These values illustrate the dependence on spot size, not a measured error in Clark's apparatus.
\Image[https://www.rc-harwell.ac.uk/sites/default/files/styles/hero/public/person-photos/Ian%20Clark-min.jpg?h=9855f42d&itok=zDA4vHSQ]
{title=Ian Clark, portrait identified on his Research Complex at Harwell profile}
{width=240}
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