Alpha Decay Q Value

Input Sources

• $E_\alpha$ and $\delta E_\alpha$: from the A record (cols 10–19, 20–21) or from the QP$From E|a= comment line.
• $A_\text{parent}$: mass number of the parent nuclide (from NUCID in the P record).

Workflow

Step 1: Read $E_\alpha$ and $\delta E_\alpha$

From the cP QP$ comment line (preferred, as it identifies the g.s.-to-g.s. transition):

219NP cP QP$From E|a=9015 keV {I16} g.s. to g.s. transition ...

Extract 9015 and 16.

Or directly from the daughter A record (cols 10–19 and 20–21).

Step 2: Identify $A_\text{parent}$

Read cols 1–3 of the P record NUCID. For 219NP P ..., $A = 219$.

Step 3: Compute and Round

Q  = round(Ea * A / (A - 4))
DQ = round(DEa * A / (A - 4))

Step 4: Write into P Record

• Cols 65–74 (index 64–73): str(Q).ljust(10)
• Cols 75–76 (index 74–75): str(DQ).ljust(2)
• Verify total line length = 80 chars.

new_line = s[:64] + str(Q).ljust(10) + str(DQ).ljust(2) + s[76:80] + '\n'

Step 5: Validate

Run ruler on the modified P record line:

python .github/scripts/ensdf_1line_ruler.py --line "modified line here"

Example

Common Errors

Notes

• For an alpha-decay chain, process each file independently; each file has its own $A_\text{parent}$.
• The P record Q field represents $Q_\alpha$ for the parent decay (g.s. to g.s.).
• Do not confuse with the daughter L-record energy (always 0 for g.s.).