The first spectrum of manganese, Mn I

In 1894, two short se ries of t hreefold spectra l tcrms wcrc d iscov cred in t he a re spcctru.'n of manganese, and in 1922 other regula ri t ies invo lving fi vcfold and s ixfold te rms were d iSco vered by Catala n who coined t he word " mul t iple t" fo r t he group of related li nes res ult lll g from combinations of such complex terms. M ult iplet a na lyses of co mplex spectra promptly led t o t he prese nt formal quan t um inte rpretation of a ll suc h ph enomena, b ut co mpa ra ble progress in the analys is of t he Mnl spectrum was ha nd lcappcd by t he p a ucity of experimental data.