JSFiddle - React, Tailwind, and code Playground

HTML

<div class="g1">
        <div class="expandable">
            <span class="tt">Source </span><span class="cc">Neutron energy was varied by changing the
                emission angle to the deuteron beam. The activities of the "2"3"7U and "2"3"1Th
                residual nuclei were measured by a Ge(Li) and a HP Ge gamma-spectrometer, respectively.</span>
        </div>
    </div>

CSS

.tt { color: #7777cc; width:150px; }
       .cc { display:inline-block;vertical-align:top;width:200px }