Portal de Periódicos da CAPES

Photo-elastic behaviour of ammonium alum crystals

1949; Wiley; Volume: 2; Issue: 1 Linguagem: Inglês

10.1107/s0365110x49000059

1600-8642

S. Bhagavantam, D. Suryanarayana,

Thermography and Photoacoustic Techniques

To test an earlier prediction by Bhagavantam, based on a group theoretical method, that the T–23 and Th–2/m {3 \overline} classes of the cubic system need four independent constants, instead of three, for describing their photo-elastic properties, crystals of ammonium alum belonging to the Th–2/m {3 \overline} class were studied completely. It was found that the crystal needs four independent constants and all the four stress-optical constants of alum have been determined. For sodium D light, they are (q11 − q12) = −5.93 × 10−13, (q11 − q13) = −5.25 × 10−13, q44 = −1.15 × 10−13, q11 = 5.5 × 10−13, q12 = 11.6 × 10−13, q13 = 10.9 × 10−13 cm.2 dyne−1. The values of the strain-optical constants are (p11 − p12) = −0.0854, (p11 − p13) = −0.0756, p44= −0.0092, p11 = 0.38, p12 = 0.46, p13= 0.45.