William Lowndes McLaughlin, 77, a research scientist with the National Institute of Standards and Technology who was a leading authority on radiation measurement, died Oct. 26 at his home in Lexington, Va. He had pancreatic cancer.

Mr. McLaughlin was best known as the father of radiochromic-dye dosimetry, a cost-effective measurement system using dye that changes color when exposed to ionizing radiation.

He wrote more than 250 scientific papers on radiation physics and was the lead author of two preeminent books in his field, "Dosimetry for Food Irradiation" and "Dosimetry for Radiation Processing."

He was also past editor of the International Journal of Applied Radiation and Isotopes, a consultant to various scientific organizations, a widely traveled lecturer and a mentor to young scientists.

In 1999, the Washington Academy of Sciences honored him for "outstanding achievement in the physical sciences."

Mr. McLaughlin worked for NIST and its predecessor agency, the National Bureau of Standards, for more than 40 years before retiring in 1996.

In retirement, he moved from his home in Washington to Lexington and became a NIST Fellow.

Mr. McLaughlin, a son of a Presbyterian minister, was born in Stony Point, Tenn., and raised in North Carolina and West Virginia.

He graduated from Hampden-Sydney College in 1949 and received a master's degree in physics from George Washington University in 1963.

He spent a year at the Tubingen University in Germany, where he was a Rotary International Fellow in physics.

He then spent about two years in the mid-1950s with the U.S. Army Signal Corps, measuring radiation at the atomic bomb test sites on Eniwetok and Bikini islands.

He was a member of the American Nuclear Society, the American Physical Society and the Cosmos Club.

Beyond his professional accomplishments, Mr. McLaughlin was a skilled guitar player who wrote more than 100 country songs and occasionally performed with his sons, both professional musicians.

His first wife, Nancy Shepherd McLaughlin, died in 1966.

Survivors include his wife of six years, Nancy Scott McLaughlin of Lexington; two sons from his first marriage, Peter McLaughlin of Tucson and David McLaughlin of Winchester, Va.; two stepsons, Theodore Kiesselbach of Minneapolis and Frederick Anderson of San Diego; two sisters; and six grandchildren.