Well, I'll be honest with you...I see essentially three questions in what you are asking but I only understand two, so that's what I will focus on. Perhaps if you rephrased the third it would be easier to help you with.
First, "store atmospherics" relates to the physical design of a retail store. It has to do with attracting customers into the store and keeping them there (thus increasing the likelihood of a purchase.) For example, have you ever been in a little shop and they have the most inappropriate music playing? Or been to a used book store that has nowhere to sit while browsing books? These are examples of atmospherics. You try to design your store to be appealing to the type of customers you are trying to attract while complementing the products you are selling.
Secondly, "purchase intention." This relates to how likely a person is to buy a particular product based on a complex set of relationships the buyer has to the item. For example, when we look at a new product we are thinking about whether we need it or not, how the product will make us look/feel, and our perceptions about the company that makes the item. Purchase intention can be built up through advertising, packaging, and using appropriate distribution channels (think of the "as seen on TV" products...some people love them, and some people would be embarrassed to own them.) \
Lastly, I am just not sure what you mean when you say "retail salesperson." Simply defined, these are the individuals who work in the store and assist us in making our purchases. Their knowledge, attitude, appearance, and accessability go a long way toward creating an atmosphere that makes people want to shop at a particular store.
Hope these helped!