Thick target yields ofL&agr; x rays (x rays/str electron) under electron bombardments from around threshold energy to 30 keV are presented for pure elements of Sn, Sm, Ta, W, Pt, Au, and Pb. The calculation ofKx‐ray yields by Green and Cosslett has been applied to the deduction ofL&agr; x‐ray yields and observed data have been compared with the calculation. A good agreement has been obtained for highZelements. An empirical formula for observedL&agr; x‐ray yieldsIL&agr;(x rays/str electron) has been found to be expressed byIL&agr;=1.3×10−7×Z1.3(UL3−1)1.46×0.938[ln(UL3−1)]2in impact energies less than 30 keV, whereUL3is the overvoltage ratio defined by the ratio of electron impact energy toL3shell ionization energy.