Dear Ms. Pennell,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located 4 series & 5 file units regarding the atomic bomb; and another series General Records Relating to Atomic Energy Matters, 1948 - 1962 in the General Records of the Department of State (Record Group 59) that may contain the information you seek. The records are not yet digitized and available in the Catalog. For access to and/or copies, please contact the National Archives at College Park - Textual Reference (RDT2) via email at firstname.lastname@example.org.
We hope this is helpful. Best of luck with your research!