Francium has no commercial applications, but because of francium's relatively simple atomic structure, among other things, it has been used in spectroscopy experiments, leading to more information regarding energy levels and the coupling constants between subatomic particles.
fɹˈænsiəm hɐz nˈoʊ kəmˈɜːʃəl ˌæplɪkˈeɪʃənz, bˌʌt bɪkˈʌz ʌv fɹˈænsiəmz ɹˈɛlətˌɪvli sˈɪmpəl ɐtˈɑːmɪk stɹˈʌktʃɚ, ɐmˌʌŋ ˈʌðɚ θˈɪŋz, ɪt hˈæzbiːn jˈuːzd ɪn spɛktɹˈɑːskəpi ɛkspˈɛɹɪmənts, lˈiːdɪŋ tə mˈoːɹ ˌɪnfɚmˈeɪʃən ɹᵻɡˈɑːɹdɪŋ ˈɛnɚdʒi lˈɛvəlz ænd ðə kˈʌplɪŋ kˈɑːnstənts bᵻtwˌiːn sˌʌbɐtˈɑːmɪk pˈɑːɹɾɪkəlz.