A New Technique for Measuring Impact‐broadened Radio Recombination Lines in HiiRegions: Confrontation with Theory at High Principal Quantum Numbers

• Published in: Publications of the Astronomical Society of the Pacific 2000-09, Vol.112 (775), p.1236-1242
• Main Authors: Bell, M. B., Avery, L. W., Seaquist, E. R., Vallée, and J. P.
• Format: Article
• Language: English
• Subjects: Contour lines; Data lines; Density; Fall lines; Inhomogeneity; Line spectra; Nebulae; Power lines; Quantum numbers; Telescopes
• ISSN: 0004-6280; 1538-3873
• DOI: 10.1086/316611

New, low‐noise receivers have allowed detection, in several giant Hiiregions, of Rydberg‐Rydberg transitions of hydrogen that cover a large range of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\Delta n$ \end{document} ‐values in a single observing window. This, in turn, allows lines covering a large range in principal quantum numbernto be detected simultaneously with the same antenna beam. We have employed a new frequency‐switching technique which allows a very precise determination of the line widths. We have used this technique with the NRAO 140 foot telescope to observe lines in W51 and Orion A near 6 GHz, with \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\Delta n$ \end{document} ‐values that vary by a factor of ∼21 ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\Delta n=1$ \end{document} –∼21) and correspondingn‐values that vary by a factor of 2.7 ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd}