Parsing XML with a URL in the root element in C#

I am having trouble parsing the following XML in C#, because of the "xmlns" attribute in the root.

<CaptureResponse xmlns="http://ift.tt/1xG5c9U">
    <CaptureResult>
        <State>Open</State>
    </CaptureResult>
</CaptureResponse>

How would I, for example, check for the existence of the element in C# with the above xml? The below does not work.

        XmlDocument doc = new XmlDocument();
        doc.LoadXml(response);
        if (doc.SelectSingleNode("CaptureResponse") != null) 
        {}