Processes.Radiative

This part of the schema describes radiative processes including spontaneous radiative decays. Also photoabsorption CrossSection is represented here. The other way to describe Collisions between photons and various objects (e.g., molecules) is in the Processes.Collisions part.

RadiativeTransition

Extension of the PrimaryType. A transition is characterized by its energy/wavelength (element EnergyWavelength) and following optional elements:

• InitialStateRef of type StateRefType, reference to the initial state of the transition,
• FinalStateRef, reference to the final state of the transition, type StateRefType),
• SpeciesRef element of type SpeciesRefType, that may be used in place of the previous two in case of unknown states. All three references may be specified, in that case states should belong to the molecule/atom, indicated by SpeciesRef.
• list of Probability elements of type RadiativeTransitionProbabilityType. Different values of probabilities may be due to different multipole orders (e.g., M1 and E2 may be possible for the same initial and final states).
• multiple SatelliteLine elements,
• multiple Broadening elements,
• list of Shifting.

EnergyWavelength

Extension of the PrimaryType, may contain multiple Wavenumber, Wavelength, Energy or Frequency elements, each of DataType. Exact nature of parameter must be determined through Method, with help of PrimaryType‘s method reference. Method’s Category element takes in this case values in (experiment, theory, ritz).

Probability

Probability element is defined as the extension of the PrimaryType. Describes parameters, relevant to transition probability. Following optional elements are possible, all of DataType if not stated otherwise:

• TransitionProbabilityA - Einstein coefficient, or transition probability.
• OscillatorStrength - Oscillator strength (dimensionless). Whether it is absorption or emission, is determined from the initial and final states of the transition.
• LineStrength - A symmetric quantity with respect to initial and final states of the transition.
• WeightedOscillatorStrength - Product of the oscillator strength and statistical weight of the initial state.
• Log10WeightedOscillatorStrength - of the WeightedOscillatorStrength.
• IdealisedIntensity - Line intensity under specific conditions. Due to its dependence on plasma parameters, this is not a universal property of a spectral line and thus should be used with care.
• Multipole of type MultipoleType - multipole order of a radiative transition (electric or magnetic). It is a string with the first upper-case symbol E or M followed by one or more digits, and the first digit cannot be 0.
• EffectiveLandeFactor - Effective Lande factor, line intensity coefficient for magneto-sensitive atomic lines.

SatelliteLine

SatelliteLine element is used to keep properties of atomic optical electron satellite lines:

Multiple SatelliteLine elements may be specified, with three optional child elements:

• DielectronicIntensityFactor
• CollisionalIntensityFactor
• BranchingRatio

each of DataType.

Broadening

Each broadening element has

• name attribute, that must contain one of the names from Lineshapes dictionary
• envRef attribute, referencing the specific environment conditions, for example, for collisional broadening.
• one or more Lineshape elements, with their respective parameters.

Normally, one broadening record should be created for each broadening mechanism and for each source (data origin). Many Lineshape elements allow to represent, for example, processing of the same experimental data with different lineshapes. Usually, there will be only one Lineshape element.

Lineshape

Lineshape in turn also has

• optional name attribute from Lineshapes dictionary, like Lorentz, Voigt, Doppler, etc.
• optional functionRef attribute of type FunctionRefType, with a reference to a Functions describing the lineshape. This attribute should be used only in case when the lineshape used in data fitting is absent in the Lineshapes dictionary
• one or more LineshapeParameter, each representing specific lineshape parameter as either a constant value or a function of environment parameters

LineshapeParameter

LineshapeParameter

either FitParameters or Value/Accuracy pair must be specified

• name attribute corresponds to one defined in Lineshapes dictionary for specific lineshape

• Value/Accuracy elements are the same as in DataType,

• FitParameters, of type FitParametersType, that allows representation of this parameter as a function of environment parameters, for example:

  <Broadening envRef="Eair-broadening-ref-env" name="pressure">
          <Lineshape name="Lorentzian">
                  <Comments>The temperature-dependent pressure broadening
                  Lorentzian lineshape</Comments>
                  <LineshapeParameter name="gammaL">
                          <FitParameters functionRef="FgammaL">
                                  <FitArgument units="K" name="T">
                                          <LowerLimit>240</LowerLimit>
                                          <UpperLimit>350</UpperLimit>
                                  </FitArgument>
                                  <FitArgument units="atm" name="p">
                                          <LowerLimit>0.</LowerLimit>
                                          <UpperLimit>1.2</UpperLimit>
                                  </FitArgument>
                                  <FitParameter name="gammaL_ref">
                                          <SourceRef>BHIT-B_HITRAN2008</SourceRef>
                                          <Value units="1/cm">0.0635</Value>
                                          <Accuracy>0.003175</Accuracy>
                                  </FitParameter>
                                  <FitParameter name="n">
                                          <SourceRef>BHIT-B_HITRAN2008</SourceRef>
                                          <Value units="unitless">0.75</Value>
                                          <Accuracy>0.15</Accuracy>
                                  </FitParameter>
                          </FitParameters>
                  </LineshapeParameter>
          </Lineshape>
  </Broadening>

Where function FgammaL is defined as follows:

<Function functionID="FgammaL">
        <Comments>This function gives the pressure- and
        temperature-dependence of the Lorentzian component of the
        pressure-broadened line width (HWHM)</Comments>
        <Expression computerLanguage="Fortran">
                gammaL_ref * p * (296./T)**n
        </Expression>
        <Y name="gammaL" units="1/cm"/>
        <Arguments>
                <Argument name="T" units="K">
                        <Description>The absolute temperature, in K</Description>
                </Argument>
                <Argument name="p" units="atm">
                        <Description>The partial pressure of the broadening species,
                                                        in atm</Description>
                </Argument>
        </Arguments>
        <Parameters>
                <Parameter name="gammaL_ref" units="1/cm">
                        <Description>The Lorentzian HWHM of the line, broadened at
                                Tref = 296 K and broadening species partial pressure
                                pref = 1atm</Description>
                </Parameter>
                <Parameter name="n" units="unitless">
                        <Description>
                                The temperature exponent of the gammaL function
                        </Description>
                </Parameter>
        </Parameters>
</Function>

Shifting

Line shifting is defined by name and/or envRef attributes. In case of linear collisional shifting, only environment is sufficient.

ShiftingParameter element is defined the same way as broadening LineshapeParameter, it is either value or function of environment parameters.

Example of a Shifting definition:

<Shifting envRef="Eair-broadening-ref-env">
        <ShiftingParameter name="delta">
                <FitParameters functionRef="Fdelta">
                        <FitArgument name="p" units="atm">
                                <LowerLimit>0.</LowerLimit>
                                <UpperLimit>1.2</UpperLimit>
                        </FitArgument>
                        <FitParameter name="delta_ref">
                                <SourceRef>BHIT-B_HITRAN2008</SourceRef>
                                <Value units="unitless">-0.001</Value>
                                <Accuracy>0.1</Accuracy>
                        </FitParameter>
                </FitParameters>
        </ShiftingParameter>
</Shifting>

CrossSection

Among with RadiativeTransition elements, Processes.Radiative processes block now has a CrossSection element, which allows description of absorption cross-section data and vibrational bands assignment in case of complex molecules.

• Description, X and Y elements describe cross-section data in tabular form, where X can be absorbed radiation frequency, wavelength or wavenumber in a form of a list of values or sequence. Y then represents a sequence of sigma values.
• Species element may have StateRef and/or SpeciesRef child elements, indicating species or specific states, to which crossection data applies.
• BandAssignment allows to indicate specific vibrational modes in cross-section data.

Example cross-sections record

Warning: DataList is truncated for clarity, originally it contains 880 space-separated numbers. You may see the original element in schema examples (tests/valid/azulene-working.xml).

<CrossSection>
        <SourceRef>B_NIST1</SourceRef>

        <Description>The IR transmittance cross section of azulene from the NIST
        Standard Reference Data Program Collection</Description>

        <X parameter="wavenumber" units="1/cm">
                <LinearSequence n="880" units="1/cm" a0="450." a1="4"/>
        </X>
        <Y parameter="sigma" units="arbitrary">
                <DataList n="880">
                        0 85 94 .. 102
                </DataList>
        </Y>

        <Species>
                <SpeciesRef>X-CUFNKYGDVFVPHO-UHFFFAOYAT</SpeciesRef>
                <StateRef>SX_Azulene-1</StateRef>
        </Species>

        <BandAssignment name="2v1+v2">
                <BandCentre>
                        <Value units="1/cm">410</Value>
                        <Accuracy>2</Accuracy>
                </BandCentre>
                <BandWidth>
                        <Value units="1/cm">40</Value>
                        <Accuracy>5</Accuracy>
                </BandWidth>
                <Modes>
                        <DeltaV modeID="V1">2</DeltaV>
                        <DeltaV modeID="V2">1</DeltaV>
                </Modes>
        </BandAssignment>
        <BandAssignment name="3v4+2v5">
                <BandCentre>
                        <Value units="1/cm">1657</Value>
                        <Accuracy>10</Accuracy>
                </BandCentre>
                <BandWidth>
                        <Value units="1/cm">120</Value>
                        <Accuracy>15.5</Accuracy>
                </BandWidth>
                <Modes>
                        <DeltaV modeID="V2">3</DeltaV>
                        <DeltaV modeID="V3">2</DeltaV>
                </Modes>
        </BandAssignment>

</CrossSection>