¹³C carrier calculator

Siemens Prisma (B₀ ≈ 2.89 T). ¹³C frequency from the session's ¹H system frequency via Ξ(¹³C) = 25.145020 %.

Inputs

¹H frequency from the protocol (MHz)

Water ¹H shift assumed for that frequency (ppm)

Target ¹³C chemical shift for the carrier (ppm)

Enter this ¹³C frequency

—MHz

Where resonances will fall (undecoupled)

Resonance	ppm	Offset from carrier (Hz)

Offsets beyond ±1.2 kHz are shown in orange: with the 0.30 ms rectangular pulse, excitation falls off beyond about that range (fitted to the phantom sweep). The sweep only sampled offsets up to about ±800 Hz.

Check an existing protocol

¹³C frequency already in the protocol (MHz)

Carrier sits at

—ppm

Formula and checks

f_TMS(¹³C) = f(¹H) / (1 + δ_water·10⁻⁶) × 0.25145020
f(¹³C) = f_TMS(¹³C) × (1 + δ_target·10⁻⁶)

Recompute every session: the ¹³C frequency is stored as a fixed number and does not follow the ¹H frequency adjustment. After acquiring, confirm that urea sits near 164.2 ppm and the glycogen C1 doublet near 97.8 / 103.2 ppm. The difference between the 4.80 and 4.68 ppm water conventions is 0.12 ppm (≈ 4 Hz at ¹³C), well under the ~46 Hz glycogen linewidth. Keep one convention for a whole study so ppm axes agree.