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')

まず stellarpop_api のドキュメントを読み、付属のスペクトル例を実行します。smooth_velocity、smooth_lsf、nebemlineinspec が恒星連続光と輝線にどのような影響を与えるかを追跡します。[OII] ダブレットを連続光を平滑化せずに狭くする、サポートされた方法を特定するか、この動作には別の変更が必要であることを文書化できれば完了です。