changing the emission line velocity width

Apologies if this information is in the documentation or in previously closed tickets, but I'd like to change (reduce) the velocity width of the emission lines without smoothing the stellar continuum. E.g., in the example below I would like to change the velocity width so the [OII] doublet is well-resolved.

According to the docs, smooth_velocity=True but smooth_lsf=False, by default, so there shouldn't be any supplemental smoothing. But clearly the lines are pretty broad (hard to tell, but I would guess >>100 km/s).

Any advice or guidance would be much-appreciated!

import fsps
import matplotlib.pyplot as plt

sp = fsps.StellarPopulation(compute_vega_mags=False, 
                            add_dust_emission=True,
                            add_neb_emission=True,
                            nebemlineinspec=True,
                            imf_type=1, # Chabrier
                            dust_type=0,
                            dust_index=-0.7,
                            sfh=0,
                            zcontinuous=1)
wave, flux = sp.get_spectrum(tage=1e-3, peraa=True)

I = (wave > 3697.) * (wave < 3757.)
fig, ax = plt.subplots()
ax.plot(wave[I], flux[I])
ax.set_xlabel('Wavelength (Angstrom)')
ax.set_ylabel('Flux')
fig.savefig('fsps-linewidth.png')

Read the stellarpop_api documentation and run the supplied spectrum example first. Trace how smooth_velocity, smooth_lsf, and nebemlineinspec affect the stellar continuum and emission lines; done means identifying a supported way to narrow the [OII] doublet without smoothing the continuum, or documenting that the behavior requires a separate change.