As an experimental physicist his main contributions concerned the passage of certain particles (pi-mesons, or pions) through solid matter and their subsequent decay.

[3][4][5][6] Within a decade of his landing in New York, Isadore had become a U.S. citizen and was running a dental laboratory at 139 Delancey Street in Manhattan.

Ashkin attended Brooklyn's James Madison High School, graduating in 1936, while still a few weeks shy of his 16th birthday.

All these men were recognized as among the finest of their generation and four of them — Fermi, Rabi, Bethe, and Lamb — were to be awarded the Nobel Prize.

Early work on the development of the atom bomb had taken place at Columbia during the six years Ashkin was an undergraduate and graduate student there.

When the process of nuclear fission was discovered in 1938, scientists in many locations in Europe and the United States began intense work to understand and control the phenomenon.

There's no information on how much, if at all, Ashkin was involved in the effort at this early stage of his career, but it is certain that the Columbia physics department was the workplace for scientists who were devoted to the secret development of a new and phenomenally powerful weapon.

With the other members of the group — Feld, Szilard, Robert F. Christy, Herbert E. Kubitschek,[35] and Seymour Bernstein (untraced) — Ashkin produced a number of technical reports on the theoretical aspects of nuclear fission.

[23][42] The group's main task was to estimate the rate at which neutrons would diffuse through the explosive core of the bomb during nuclear fission.

[43] Welton, however, told of the group's long hard hours, high spirits and cohesiveness, and said they achieved some excellent successes in theoretical physics.

In fact, their assistant, an enlisted man named Murray Peshkin, remembered the group as having an unending need for calculation.

It helped that some of the married ones were able to bring their wives to live in the town of Los Alamos and thus parties of men and women could get together for social activities.

A Met Lab colleague remembered playing touch football with him and Feld on an open space called the midway at the University of Chicago.

He took pride in deceiving the mail censors, guessing the combinations of safes in which secret files were stored, picking door locks, and teasing the guards (he would depart from the main gate, circle around the perimeter to a hole in the fence, re-enter the facility, and then exit the gate again, thus causing confusion and consternation both.)

He also liked to pound his bongo drums, a practice which made those within hearing range grit their teeth but which he believed put him in touch with the spirits of the Indians who formerly inhabited the place.

Feynman wasn't unusual in his affection for drumming but his choice of musical genres was atypical as was his lack of skill as a drummer.

When Ashkin played the recorder, Feynman said he was using "an infernally popular wooden tube ... for making noises bearing a one-one correspondence to black dots on a piece of paper -- in imitation to music.

The program was styled the "Los Alamos University" and some junior members of laboratory personnel received college credit for attending them.

January 21, 1947 (extract from abstract: "Convenient approximate methods are developed for the calculation of critical sizes and multiplication rates of spherical, active cores surrounded by infinite tampers.

[40] In 1950 it was revealed that one of the scientists at Los Alamos, Klaus Fuchs, was providing the Soviet intelligence bureau, NKGB, with secret information about bomb research.

As an assistant professor he taught mechanics and thermodynamics and theoretical physics and performed pioneering experiments on neutron-proton, proton-proton, and nucleon-nucleon scattering.

Feynman devised the diagram in 1948 to provide a simple visualization of the mathematical expressions governing the behavior of subatomic particles.

The cyclotron remained in use at the Saxonburg Nuclear Research Center until the mid-1970s when it was dismantled and, using it, Ashkin was able to produce some of his best-known experimental results.

[30][71] Using the CIT cyclotron and following on work done by Bethe and Robert E. Marshak, Ashkin conducted experiments to determine the characteristics of a short-lived particle — the pi-meson or pion — that is produced when high energy cosmic ray protons and other cosmic ray components interact with matter in the Earth's atmosphere.

[73] In 1958–1959 Ashkin won a Ford Foundation grant to spend a sabbatical year in Geneva, Switzerland, at CERN, the European Organization for Nuclear Research.

[75] Using this particle accelerator he helped to make a significant discovery which confirmed an aspect of the V-A Theory of weak interactions.