Sentence:  In addition to the basic programs in wavelength standards , spectroscopy , <WSD>solid</WSD> state physics , interactions of the free electron and atomic constants which are necessary to provide the foundation for technological progress , the Bureau has strengthened its activities in laboratory astrophysics . 
Meaning of the word marked with <WSD> tags:  characteristic of or relating to the physical properties of solid materials especially electromagnetic or thermodynamic or structural properties of crystalline solids