Illustrated Glossary of Organic Chemistry

M+1: In mass spectrometry the molecular ion whose mass is one higher than M.

Molecular ion region of the mass spectrum of 1-chlorodecane (C₁₀H₂₁Cl).
The relative abundance of M is due to ¹²C₁₀¹H₂₁³⁵Cl.
The relative abundance of M+1 is due to ¹²C₉¹³C¹H₂₁³⁵Cl + ¹²C₁₀¹H₂₀²H³⁵Cl.
The relative abundance of M+2 is due to ¹²C₉¹⁴C¹H₂₁³⁵Cl + ¹²C₈¹³C₂¹H₂₁³⁵Cl + ¹²C₉¹³C¹H₂₀²H³⁵Cl + ¹²C₁₀¹H₁₉²H₂³⁵Cl + ¹²C₁₀¹H₁₉³H³⁵Cl + ¹²C₁₀¹H₂₁³⁷Cl.