A tetrahedral MCl<sub>4</sub> type molecule in which M is isotopically pure and Cl is in natural abundance consists of five isotopic species due to the mixing of the <sup>35</sup>Cl (75.4%) and <sup>37</sup>Cl (24.6%) isotopes. Table I lists their symmetry, percent natural abundances, and symmetry species of infrared active modes corresponding to the <i>v</i><sub>3</sub> vibration of the T<sub>d</sub> molecule. The <i>v</i><sub>3</sub> bands of CCl<sub>4</sub> and <sup>28</sup>SiCl<sub>4</sub> in argon matrices exhibit "five-peak chlorine isotope patterns" due to overlap of the nine bands listed in Table I. The vertical lines shown in Fig. 1A' indicate such a pattern for <sup>74</sup>GeCl<sub>4</sub>.
David Tevault, J. David Brown, and Kazuo Nakamoto, "Matrix-Isolation Infrared and Computer-Simulation Spectra (v3 Bands) of GeCl4, GeBr4, and GeI4 in Argon Matrices," Appl. Spectrosc. 30, 461-462 (1976)