Radiative lineshapes, broadening and shifting¶

Radiative element now has, among all other, two new elements, called Broadening and Shifting Those elements may be specified more than once to represent different broadening/shifting processes.

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 function 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

FitParameters 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>

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