Isotope Shift in Boron

Mrozowski's microphotometer curves for the lines λ2497, 2498 of B I due to 2²P1/2,11/2-3²S1/2 and λ3451 of B II due to (2s)(2p)¹P₁-(2p)²¹D₂ showed asymmetries which he resolved into isotope shifts arising from the isotopes 10 and 11. Subtraction of the corresponding normal shift from each of his observed values leads to observed specific shifts of -0.373 cm^-1 for λ2497, -0.366 cm^-1 for λ2498, and +0.734 cm^-1 for λ3451. The present note gives a calculation of these specific shifts with the aid of Morse, Young, Haurwitz wave functions. The results are -0.3665 cm^-1 for either member of λ2497, 2498 of B I and +0.566 cm^-1 for λ3451 of B II. Reasons are suggested why the agreement with experiment is better in the case of the B I lines than in the case of the B II line, and also why the present calculation for the B I lines agrees better than that due to Opechowski and DeVries, who calculated -0.33 cm^-1 for λ2497, 2498. The possible spread due to nuclear spin is estimated with the use of triplet separations and Morse, Young, Haurwitz functions and found to be of the order 0.03 cm^-1 in each case, thus explaining on the basis of smallness the absence of nuclear spin h.f.s. in Mrozowski's plates.