In the double-slit experiment with single molecules or atoms, several conditions are required to observe the interference pattern. Here are the key conditions:
Single-particle source: It is crucial to have a controlled source that emits single particles (molecules or atoms) one at a time. This can be achieved using techniques such as electromagnetically trapping and cooling atoms or using specialized sources that emit particles one by one.
Narrow slits: The two slits through which the particles pass must be narrow and closely spaced. Ideally, the slits should be comparable in size to the de Broglie wavelength of the particles. This ensures that the particles can exhibit wave-like behavior and interfere with each other.
Coherence: The particles emitted from the source must be coherent. Coherence refers to the property of the particles having a well-defined phase relationship with each other. This can be achieved by carefully controlling the source and minimizing any phase disturbances.
Well-defined path lengths: The paths that the particles take from the source to the screen or detector must have well-defined and comparable lengths. Any significant difference in path lengths can disrupt the interference pattern.
Detector placement: The screen or detector where the particles are detected should be placed in a way that allows the interference pattern to form. This typically involves placing the screen at a sufficient distance from the double slits to allow the wavefronts to spread out and overlap.
Isolation from the environment: As you mentioned, isolation from the environment is essential to minimize any external disturbances that could disrupt the interference pattern. This includes reducing vibrations, air currents, and other forms of interaction that can cause decoherence.
By satisfying these conditions, it becomes possible to observe the interference pattern in the double-slit experiment even with single molecules or atoms. The pattern arises due to the wave-like behavior of particles and their ability to interfere constructively or destructively as they pass through the slits.