Patent Number: 
Section: claims

1. A multilayered spectroscopic device for use in fluorescent X-ray analysis of boron (B) contained in a sample, which device comprises a plurality of layer pairs, each pair including a reflecting layer and a spacer layer, that are laminated on a substrate; wherein lanthanum (La), an alloy containing lanthanum as a principal component or lanthanum oxide (La 2 O 3 ) is used as material for the reflecting layers, and boron is used as material for the spacer layers, a periodic length is chosen to be within the range of 7 to 14 nm and a film thickness ratio of the reflecting layers relative to the spacer layers is chosen to be within the range of 2/3 to 3/2; and  wherein the multilayered spectroscopic device has a total laminated film thickness sufficient to allow a strength of reflection of B-Kxcex1 line to attain a value equal to or higher than 98% of a saturation value. 2. The multilayered spectroscopic device for use in fluorescent X-ray analysis of boron as claimed in  claim 1 , wherein the total laminated film thickness is chosen to be within the range of 280 to 320 nm. claim 1 3. The multilayered spectroscopic device for use in fluorescent X-ray analysis of boron as claimed in  claim 1 , wherein the film thickness ratio of the reflecting layers relative to the spacer layer is chosen to be within the range of 4/5 to 5/4. claim 1