WASHINGTON — Preservation scientists at the Library of Congress have discovered that Thomas Jefferson, even in the act of declaring independence from England, had trouble breaking free from monarchial rule.

In an early draft of the Declaration of Independence, Jefferson wrote the word “subjects,’’ when he referred to the American public. He then erased that word and replaced it with “citizens,’’ a term he used frequently throughout the final draft.

The Library released news of the struck word yesterday.

Fenalla France, a research chemist at the Library, said her lab made the discovery last year by using hyperspectral imaging, a high resolution digital camera that compiles a series of images to highlight layers of a document. Some of those invisible layers — like erased text — pop into view on a computer screen.

France said it appears Jefferson used his hand to wipe the word “subjects’’ out while the ink was still wet. A distinct brown smudge is apparent on the paper, although the word itself is not legible without the help of the digital technology.

“It shows the progress of his mind,’’ said James Billington, librarian of Congress. “This was a decisive moment.’’

The document is normally kept under lock and key in one of the Library’s vaults. Yesterday morning it traveled under police escort for a demonstration of the high-tech imaging, where Maria Nugent, director of the Library’s top treasures collection, revealed the rough draft of the Declaration, which includes handwritten corrections by John Adams and Benjamin Franklin.

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