Table 1.

Definitions for variables and descriptive terms.

Variable	Definition
D	diffusion coefficient
kb	Boltzmann’s constant
T	Temperature
K	ion mobility
E	elementary charge
td	Measured drift time
Δt	width at half maximum of intensity peak (in time)
E	drift field
L	drift region total length
ΔL	width at half maximum of intensity peak (in length)
RIMS	resolving power for IMS
ROMS	resolving power for OMS
d	OMS drift region segment
dt	ion transmission region of d
lt	length of the ion transmission region of d
de	ion elimination region of d
le	ion elimination region of d
n	number of d regions in OMS separation device (positive integers)
ϕ	OMS system phase (positive integers)
m	harmonic frequency number (determined by ϕ and h)
j	index for field array regions in ion trajectory simulations (zero and positive integers)
h	index to relate OMS phase and harmonic frequency (positive integers)
$\sqrt{\overline{r^2}}$	root mean square ion displacement due to mobility
θ	randomization angle for ion trajectory simulations
Pw1	pulse width corresponding with the OMS peak apex frequency setting
Pw2	pulse width corresponding with the base of the OMS peak frequency setting
ff	fundamental frequency determined from the time required for an ion to travers a single d region
fm	harmonic field application frequency setting
f1	frequency setting corrresponding with the apex of the OMS peak
f2	frequency setting corresponding with the base of the OMS peak
ΔfFWHM	full width at half maximum peak height of the OMS peak
vdif	velocity due to ion diffusion, in this case directed against mobility
σ	standard deviation of the OMS peak using the peak apex as the mean
C1	a constant associated with converting standard deviation into FWHM of a guassian distribution
C2	a constant associated with converting the diffusion term in the ROMS equation with RIMS
Ω	ion collision cross section
P	buffer gas pressure
mI	mass of the ion
mB	mass of the buffer gas
N	neutral number density under STP conditions