Read the output, preserve the calculation
Excitation Studio reads Gaussian text output: excited-state energies, wavelengths, oscillator strengths, orbital coefficients, electric and magnetic transition dipoles, and length/velocity rotatory strengths. Repeated excitation sets are kept separate. Choose the set you want to inspect.
Broadening & units
FWHM and energy shifts are specified in eV. Broadening is performed in energy space, then sampled on the selected horizontal axis. Axis changes do not apply a density Jacobian. Transition sticks show isolated broadened-band peak heights on the same ordinate as the curve.
FL / CPL emission mode
Emission mode uses Gaussian excited state 1 only, independently of the state selected in the table. Use transition properties from a calculation at the emitting-state geometry. FL and CPL are relative photon-emission envelopes, not molar absorptivity or absolute quantum yields. Both FL and CPL intensities are multiplied by 1000 for readability, including curve CSV exports and overlap/sum plots. UV/ECD scaling is unchanged. Normalize divides each curve by its maximum absolute intensity, so normalized peaks remain 1. The transition energy is taken from the output; no excited-state relaxation is inferred.
Overlap & Sum
With two or more files loaded, Overlap compares one selected excitation set per file. Choose the channel or Both, and use Files & excitation sets to select each file’s calculation. Sum adds the raw curves with equal weight before any final normalization, retaining signed ECD/CPL cancellation. FL/CPL uses state 1 independently for each file. Missing contributions are reported as unavailable or partial. The active calculation still controls the table and molecular view.
SVG exports the displayed overlap or sum with its file legend. Curve CSV buttons export the sum in Sum view, or the explicitly labelled active file in individual overlap view. Each CSV retains exactly two columns and the 0.5 nm wavelength grid. JSON records the contributing files, selected sets, curves and normalization.
CSV downloads
Each curve CSV contains exactly two columns: wavelength_nm and the chosen spectrum’s intensity (epsilon, delta_epsilon, FL_relative_intensity, or CPL_relative_intensity). UV/ECD and FL/CPL have separate download options. Wavelengths use a 0.5 nm grid within the current plot window, regardless of the displayed horizontal axis. The oscillator-strength CSV also contains just two columns: wavelength_nm and oscillator_strength_f. Emission exports include state 1 only.
Selected-state properties
The selected-state panel calculates |μ|, |m|, D = |μ|², G = |m|², cos θ, θ, g, and vector-derived R from the length-gauge electric and magnetic transition moments. Magnitudes are shown in 10⁻²⁰ esu cm and 10⁻²⁰ erg G⁻¹; squared strengths use the corresponding 10⁻⁴⁰ units. These derived values always use the length gauge, independently of the raw-component gauge selector.
Let q be the normalized dot product of the printed electric and magnetic vectors. UV/ECD uses cos θ = q and g = −4|μ||m|q/(D + G). FL/CPL uses cos θ = −q and g = 4|μ||m|cos θ/(D + G). Thus the angles are supplementary, while g and vector-derived R = −|μ||m|q are identical for the same geometry. Gaussian’s printed R remains separate and is used for the spectral curves. Broadening, shifts, and normalization do not change these selected-state properties.
Molecular structure & transition vectors
The 3D view uses the Cartesian orientation printed before the selected excitation set, with standard orientation preferred when available. It follows the selected table row and always uses the length-gauge electric transition moment. UV/ECD draws both vectors with their printed signs. FL/CPL reverses only the magnetic vector. Raw moments and printed rotatory strengths are preserved.
Arrow components and magnitudes remain in Gaussian’s printed a.u.; no cgs conversion is used in this view. Positive display gains change arrow lengths for visibility without changing direction or the reported a.u. values. The arrows share an origin at the geometric center of the molecule for display; nuclear coordinates are in Å and inferred bonds are visual guides. Drag to rotate, scroll to zoom, or use the keyboard controls. If the output lacks readable Cartesian coordinates, only the available vectors are shown.
The XYZ axes checkbox controls coordinate-axis visibility. Download PNG saves the current drawing at twice its displayed pixel dimensions, with the current camera and visible objects. Download BILD saves a .bild 3D drawing for ChimeraX (File → Open): visible atoms, inferred bonds, vectors, and axes are included in the original Gaussian coordinate frame. Arrow gains and the FL/CPL magnetic reversal are retained. The BILD drawing can be rotated in ChimeraX; the browser camera is not applied to its coordinates. BILD content → Vectors only exports just the visible electric/magnetic arrows, omitting atoms, bonds and XYZ axes while preserving the centroid origin and display gains. It changes only the BILD file, leaving the live molecule and PNG unchanged.
Interpreting the details
Dipole components use the atomic units printed by Gaussian. Rotatory strengths use 10⁻⁴⁰ cgs (esu² cm²). Orbital contributions after “c =” are displayed as 2c² × 100% for unlabelled closed-shell transitions, or c² × 100% for A/B-labelled alpha/beta spin-orbital transitions. Each percentage is calculated independently, without renormalization over the printed contributions. The original signed coefficients are preserved in CSV/JSON exports and shown on hover. Missing properties are shown as “not printed” and are never inferred from unrelated calculations.
The demo uses the provided Gaussian calculation demo.log, with 35 excited states and 78 atoms. Spectra are predictions broadened from discrete transitions, not experimental measurements. Excited-state absorption calculations and nonstandard output variants require independent validation.
References
