Model & Assumptions Beta
- Model
- Exact Mie: σpr = σext − gσsca with g = ⟨cosθ⟩ from the Mie coefficients (Bohren & Huffman §4.5); F = nhostσprI/c. Trap: Rayleigh (dipole) gradient force in a TEM₀₀ Gaussian focus — U = −βI with β = (2πnhosta³/c)·Re[(m²−1)/(m²+2)]; κr = 4βI₀/w₀², κz = 2βI₀/zR².
- Assumptions
- Homogeneous sphere; paraxial Gaussian beam (peak irradiance 2P/πw₀²); Minkowski photon momentum in the host medium. Trap numbers use the dipole approximation — trusted for 2a ≲ λ/(5nhost), flagged otherwise.
- Limitations
- No generalized Lorenz–Mie (beam-shape) coefficients: outside the dipole regime, stiffness and depth are indicative only. Gradient force uses Re(n) of absorbing particles; heating of absorbing particles is the Photothermal tool's job.