How was the Collisional Cross Section (CCS) Area converted?

[Xisong-Feng]

Dear developers,

Thanks for your contribution! I wonder how TIMSCONVERT processes mobility data and converts it to CCS. I could not directly get the CCS values while analyzing .d file in DataAnalysis (Bruker). But if using Mason-Schamp equation, the temperature, pressure parameters are needed.

Here is part of .mzML file converted from .d file with TIMSCONVERT:

        </spectrum>
        <spectrum index="57" defaultArrayLength="318" id="scan=58">
          <cvParam cvRef="PSI-MS" accession="MS:1000580" name="MSn spectrum" value=""/>
          <cvParam cvRef="PSI-MS" accession="MS:1000511" name="ms level" value="2"/>
          <cvParam cvRef="PSI-MS" accession="MS:1000285" name="total ion current" value="52640.0"/>
          <cvParam cvRef="PSI-MS" accession="MS:1000504" name="base peak m/z" value="922.000391219724" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
          <cvParam cvRef="PSI-MS" accession="MS:1000505" name="base peak intensity" value="10201.0" unitCvRef="PSI-MS" unitAccession="MS:1000131" unitName="number of detector counts"/>
          <cvParam cvRef="PSI-MS" accession="MS:1000527" name="highest observed m/z" value="3644.167037930458" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
          <cvParam cvRef="PSI-MS" accession="MS:1000528" name="lowest observed m/z" value="212.91226544599297" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
          <cvParam cvRef="PSI-MS" accession="MS:1000127" name="centroid spectrum" value=""/>
          <scanList count="1">
            <cvParam cvRef="PSI-MS" accession="MS:1000795" name="no combination" value=""/>
            <scan>
              <cvParam cvRef="PSI-MS" accession="MS:1000016" name="scan start time" value="0.2214469166666667" unitCvRef="PSI-MS" unitAccession="UO:0000031" unitName="minute"/>
            </scan>
          </scanList>
          <precursorList count="1">
            <precursor spectrumRef="scan=57">
              <isolationWindow>
                <cvParam cvRef="PSI-MS" accession="MS:1000827" name="isolation window target m/z" value="922.4794643634797" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
                <cvParam cvRef="PSI-MS" accession="MS:1000828" name="isolation window lower offset" value="1.5" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
                <cvParam cvRef="PSI-MS" accession="MS:1000829" name="isolation window upper offset" value="1.5" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
              </isolationWindow>
              <selectedIonList count="1">
                <selectedIon>
                  <cvParam cvRef="PSI-MS" accession="MS:1000744" name="selected ion m/z" value="921.9991952548357" unitCvRef="PSI-MS" unitAccession="MS:1000040" unitName="m/z"/>
                  <cvParam cvRef="PSI-MS" accession="MS:1000042" name="peak intensity" value="97668.0" unitCvRef="PSI-MS" unitAccession="MS:1000131" unitName="number of detector counts"/>
                  <cvParam cvRef="PSI-MS" accession="MS:1000041" name="charge state" value="1"/>
                  <cvParam cvRef="PSI-MS" accession="MS:1002815" name="inverse reduced ion mobility" value="1.1722180584176698" unitCvRef="PSI-MS" unitAccession="MS:1002814" unitName="volt-second per square centimeter"/>
                  <cvParam cvRef="PSI-MS" accession="MS:1002954" name="collisional cross sectional area" value="238.2748434174985" unitCvRef="PSI-MS" unitAccession="UO:0000324" unitName="square angstrom"/>
                </selectedIon>
              </selectedIonList>
...